From b11bb0813ea55f26544b653782fb3afec5503bf0 Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Sat, 2 Jan 2021 22:16:17 +0100
Subject: [PATCH 01/22] Add first implementation of a mercurial resolver

---
 src/config.cr       |   1 +
 src/resolvers/hg.cr | 463 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 464 insertions(+)
 create mode 100644 src/resolvers/hg.cr

diff --git a/src/config.cr b/src/config.cr
index e41d070e..a1cbfd9a 100644
--- a/src/config.cr
+++ b/src/config.cr
@@ -12,6 +12,7 @@ module Shards
   VERSION_REFERENCE     = /^v?\d+[-.][-.a-zA-Z\d]+$/
   VERSION_TAG           = /^v(\d+[-.][-.a-zA-Z\d]+)$/
   VERSION_AT_GIT_COMMIT = /^(\d+[-.][-.a-zA-Z\d]+)\+git\.commit\.([0-9a-f]+)$/
+  VERSION_AT_HG_COMMIT  = /^(\d+[-.][-.a-zA-Z\d]+)\+hg\.commit\.([0-9a-f]+)$/
 
   def self.cache_path
     @@cache_path ||= find_or_create_cache_path
diff --git a/src/resolvers/hg.cr b/src/resolvers/hg.cr
new file mode 100644
index 00000000..8e35e94d
--- /dev/null
+++ b/src/resolvers/hg.cr
@@ -0,0 +1,463 @@
+require "uri"
+require "./resolver"
+require "../versions"
+require "../logger"
+require "../helpers"
+
+module Shards
+  abstract struct HgRef < Ref
+    def full_info
+      to_s
+    end
+  end
+
+  struct HgBranchRef < HgRef
+    def initialize(@branch : String)
+    end
+
+    def to_hg_ref(simple = false)
+      simple ? @branch : "branch(\"#{@branch}\") and head()"
+    end
+
+    def to_s(io)
+      io << "branch " << @branch
+    end
+
+    def to_yaml(yaml)
+      yaml.scalar "branch"
+      yaml.scalar @branch
+    end
+  end
+
+  struct HgBookmarkRef < HgRef
+    def initialize(@bookmark : String)
+    end
+
+    def to_hg_ref(simple = false)
+      simple ? @bookmark : "bookmark(\"#{@bookmark}\")"
+    end
+
+    def to_s(io)
+      io << "bookmark " << @bookmark
+    end
+
+    def to_yaml(yaml)
+      yaml.scalar "bookmark"
+      yaml.scalar @bookmark
+    end
+  end
+
+  struct HgTagRef < HgRef
+    def initialize(@tag : String)
+    end
+
+    def to_hg_ref(simple = false)
+      simple ? @tag : "tag(\"#{@tag}\")"
+    end
+
+    def to_s(io)
+      io << "tag " << @tag
+    end
+
+    def to_yaml(yaml)
+      yaml.scalar "tag"
+      yaml.scalar @tag
+    end
+  end
+
+  struct HgCommitRef < HgRef
+    getter commit : String
+
+    def initialize(@commit : String)
+    end
+
+    def =~(other : HgCommitRef)
+      commit.starts_with?(other.commit) || other.commit.starts_with?(commit)
+    end
+
+    def to_hg_ref(simple = false)
+      @commit
+    end
+
+    def to_s(io)
+      io << "commit " << @commit[0...7]
+    end
+
+    def full_info
+      "commit #{@commit}"
+    end
+
+    def to_yaml(yaml)
+      yaml.scalar "commit"
+      yaml.scalar @commit
+    end
+  end
+
+  struct HgCurrentRef < HgRef
+    def to_hg_ref(simple = false)
+      "."
+    end
+
+    def to_s(io)
+      io << "current"
+    end
+
+    def to_yaml(yaml)
+      raise NotImplementedError.new("HgCurrentRef is for internal use only")
+    end
+  end
+
+  class HgResolver < Resolver
+    @@has_hg_command : Bool?
+    @@hg_version : String?
+
+    @origin_url : String?
+
+    def self.key
+      "hg"
+    end
+
+    def self.normalize_key_source(key : String, source : String) : {String, String}
+      case key
+      when "hg"
+        {"hg", source}
+      else
+        raise "Unknown resolver #{key}"
+      end
+    end
+
+    protected def self.has_hg_command?
+      if @@has_hg_command.nil?
+        @@has_hg_command = (Process.run("hg", ["--version"]).success? rescue false)
+      end
+      @@has_hg_command
+    end
+
+    protected def self.hg_version
+      @@hg_version ||= `hg --version`[/\(version\s+([^)]*)\)/, 1]
+    end
+
+    def read_spec(version : Version) : String?
+      update_local_cache
+      ref = hg_ref(version)
+
+      if file_exists?(ref, SPEC_FILENAME)
+        capture("hg cat -r #{Process.quote(ref.to_hg_ref)} #{Process.quote(SPEC_FILENAME)}")
+      else
+        Log.debug { "Missing \"#{SPEC_FILENAME}\" for #{name.inspect} at #{ref}" }
+        nil
+      end
+    end
+
+    private def spec_at_ref(ref : HgRef) : Spec?
+      update_local_cache
+      begin
+        if file_exists?(ref, SPEC_FILENAME)
+          spec_yaml = capture("hg cat -r #{Process.quote(ref.to_hg_ref)} #{Process.quote(SPEC_FILENAME)}")
+          Spec.from_yaml(spec_yaml)
+        end
+      rescue Error
+        nil
+      end
+    end
+
+    private def spec?(version)
+      spec(version)
+    rescue Error
+    end
+
+    def available_releases : Array(Version)
+      update_local_cache
+      versions_from_tags
+    end
+
+    def latest_version_for_ref(ref : HgRef?) : Version
+      update_local_cache
+      ref ||= HgCurrentRef.new
+      begin
+        commit = commit_sha1_at(ref)
+      rescue Error
+        raise Error.new "Could not find #{ref.full_info} for shard #{name.inspect} in the repository #{source}"
+      end
+
+      if spec = spec_at_ref(ref)
+        Version.new "#{spec.version.value}+hg.commit.#{commit}"
+      else
+        raise Error.new "No #{SPEC_FILENAME} was found for shard #{name.inspect} at commit #{commit}"
+      end
+    end
+
+    def matches_ref?(ref : HgRef, version : Version)
+      case ref
+      when HgCommitRef
+        ref =~ hg_ref(version)
+      when HgBranchRef, HgBookmarkRef, HgCurrentRef
+        # TODO: check if version is the branch
+        version.has_metadata?
+      else
+        # TODO: check branch and tags
+        true
+      end
+    end
+
+    protected def versions_from_tags
+      capture("hg tags --template '{tag}\\n'")
+        .split('\n')
+        .sort!
+        .compact_map { |tag| Version.new($1) if tag =~ VERSION_TAG }
+    end
+
+    def matches?(commit)
+      if branch = dependency["branch"]?
+        !capture("hg log -r 'branch(#{tag}) and descendants(#{commit})' --template '{branch}\\n'").strip.empty?
+      elsif bookmark = dependency["bookmark"]?
+        !capture("hg log -r 'bookmark(#{bookmark}) and descendants(#{commit})' --template '{bookmarks}\\n'").strip.empty?
+      elsif tag = dependency["tag"]?
+        !capture("hg log -r 'tag(#{tag}) and descendants(#{commit})' --template '{tags}\n'").strip.empty?
+      else
+        !capture("hg log -r #{commit}").strip.empty?
+      end
+    end
+
+    def install_sources(version : Version, install_path : String)
+      update_local_cache
+      ref = hg_ref(version)
+
+      FileUtils.rm_r(install_path) if File.exists?(install_path)
+      Dir.mkdir_p(install_path)
+      run "hg clone --quiet -u #{Process.quote(ref.to_hg_ref(true))} -- #{Process.quote(local_path)} #{Process.quote(install_path)}"
+    end
+
+    def commit_sha1_at(ref : HgRef)
+      capture("hg log -r #{Process.quote(ref.to_hg_ref)} --template '{node}'").strip
+    end
+
+    def local_path
+      @local_path ||= begin
+        uri = parse_uri(hg_url)
+
+        path = uri.path
+        path = Path[path]
+        # E.g. turns "c:\local\path" into "c\local\path". Or just drops the leading slash.
+        if (anchor = path.anchor)
+          path = Path[path.drive.to_s.rchop(":"), path.relative_to(anchor)]
+        end
+
+        if host = uri.host
+          File.join(Shards.cache_path, host, path)
+        else
+          File.join(Shards.cache_path, path)
+        end
+      end
+    end
+
+    def hg_url
+      source.strip
+    end
+
+    def parse_requirement(params : Hash(String, String)) : Requirement
+      params.each do |key, value|
+        case key
+        when "branch"
+          return HgBranchRef.new value
+        when "bookmark"
+          return HgBookmarkRef.new value
+        when "tag"
+          return HgTagRef.new value
+        when "commit"
+          return HgCommitRef.new value
+        else
+        end
+      end
+
+      super
+    end
+
+    record HgVersion, value : String, commit : String? = nil
+
+    private def parse_hg_version(version : Version) : HgVersion
+      case version.value
+      when VERSION_REFERENCE
+        HgVersion.new version.value
+      when VERSION_AT_HG_COMMIT
+        HgVersion.new $1, $2
+      else
+        raise Error.new("Invalid version for hg resolver: #{version}")
+      end
+    end
+
+    private def hg_ref(version : Version) : HgRef
+      hg_version = parse_hg_version(version)
+      if commit = hg_version.commit
+        HgCommitRef.new commit
+      else
+        HgTagRef.new "v#{hg_version.value}"
+      end
+    end
+
+    private def update_local_cache
+      if cloned_repository? && origin_changed?
+        delete_repository
+        @updated_cache = false
+      end
+
+      return if Shards.local? || @updated_cache
+      Log.info { "Fetching #{hg_url}" }
+
+      if cloned_repository?
+        # repositories cloned with shards v0.8.0 won't fetch any new remote
+        # refs; we must delete them and clone again!
+        if valid_repository?
+          fetch_repository
+        else
+          delete_repository
+          mirror_repository
+        end
+      else
+        mirror_repository
+      end
+
+      @updated_cache = true
+    end
+
+    private def mirror_repository
+      hg_retry(err: "Failed to clone #{hg_url}") do
+        # We checkout the working directory so that "." is meaningful.
+        #
+        # An alternative would be to use the `@` bookmark, but only as long
+        # as nothing new is committed.
+        run_in_current_folder "hg clone --quiet -- #{Process.quote(hg_url)} #{Process.quote(local_path)}"
+      end
+    end
+
+    private def fetch_repository
+      hg_retry(err: "Failed to update #{hg_url}") do
+        run "hg pull"
+      end
+    end
+
+    private def hg_retry(err = "Failed to update repository")
+      retries = 0
+      loop do
+        yield
+        break
+      rescue Error
+        retries += 1
+        next if retries < 3
+        raise Error.new(err)
+      end
+    end
+
+    private def delete_repository
+      Log.debug { "rm -rf #{Process.quote(local_path)}'" }
+      Shards::Helpers.rm_rf(local_path)
+      @origin_url = nil
+    end
+
+    private def cloned_repository?
+      Dir.exists?(local_path)
+    end
+
+    private def valid_repository?
+      File.each_line(File.join(local_path, ".hg", "dirstate")) do |line|
+        return true if line =~ /mirror\s*=\s*true/
+      end
+      false
+    end
+
+    private def origin_url
+      @origin_url ||= capture("hg paths default").strip
+    end
+
+    # Returns whether origin URLs have differing hosts and/or paths.
+    protected def origin_changed?
+      return false if origin_url == hg_url
+      return true if origin_url.nil? || hg_url.nil?
+
+      origin_parsed = parse_uri(origin_url)
+      hg_parsed = parse_uri(hg_url)
+
+      (origin_parsed.host != hg_parsed.host) || (origin_parsed.path != hg_parsed.path)
+    end
+
+    # Parses a URI string, with additional support for ssh+git URI schemes.
+    private def parse_uri(raw_uri)
+      # Need to check for file URIs early, otherwise generic parsing will fail on a colon.
+      if (path = raw_uri.lchop?("file://"))
+        return URI.new(scheme: "file", path: path)
+      end
+
+      # Try normal URI parsing first
+      uri = URI.parse(raw_uri)
+      return uri if uri.absolute? && !uri.opaque?
+
+      # Otherwise, assume and attempt to parse the scp-style ssh URIs
+      host, _, path = raw_uri.partition(':')
+
+      if host.includes?('@')
+        user, _, host = host.partition('@')
+      end
+
+      # Normalize leading slash, matching URI parsing
+      unless path.starts_with?('/')
+        path = '/' + path
+      end
+
+      URI.new(scheme: "ssh", host: host, path: path, user: user)
+    end
+
+    private def file_exists?(ref : HgRef, path)
+      files = capture("hg files -r #{Process.quote(ref.to_hg_ref)} -- #{Process.quote(path)}")
+      !files.strip.empty?
+    end
+
+    private def capture(command, path = local_path)
+      run(command, capture: true, path: path).not_nil!
+    end
+
+    private def run(command, path = local_path, capture = false)
+      if Shards.local? && !Dir.exists?(path)
+        dependency_name = File.basename(path)
+        raise Error.new("Missing repository cache for #{dependency_name.inspect}. Please run without --local to fetch it.")
+      end
+      Dir.cd(path) do
+        run_in_current_folder(command, capture)
+      end
+    end
+
+    private def run_in_current_folder(command, capture = false)
+      unless HgResolver.has_hg_command?
+        raise Error.new("Error missing hg command line tool. Please install Mercurial first!")
+      end
+
+      Log.debug { command }
+
+      output = capture ? IO::Memory.new : Process::Redirect::Close
+      error = IO::Memory.new
+      status = Process.run(command, shell: true, output: output, error: error)
+
+      if status.success?
+        output.to_s if capture
+      else
+        str = error.to_s
+        if str.starts_with?("abort: ") && (idx = str.index('\n'))
+          message = str[7...idx]
+        else
+          message = str
+        end
+        raise Error.new("Failed #{command} (#{message}). Maybe a commit, branch, bookmark or file doesn't exist?")
+      end
+    end
+
+    def report_version(version : Version) : String
+      hg_version = parse_hg_version(version)
+      if commit = hg_version.commit
+        "#{hg_version.value} at #{commit[0...7]}"
+      else
+        version.value
+      end
+    end
+
+    register_resolver "hg", HgResolver
+  end
+end

From c1a6c2dca8da5de217cdefdbd8e0c2ca78d5227e Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Sat, 2 Jan 2021 22:21:48 +0100
Subject: [PATCH 02/22] Add specs for hg resolver

---
 spec/support/factories.cr     |  86 +++++++++++++++++++
 spec/support/requirement.cr   |   4 +
 spec/unit/hg_resolver_spec.cr | 153 ++++++++++++++++++++++++++++++++++
 3 files changed, 243 insertions(+)
 create mode 100644 spec/unit/hg_resolver_spec.cr

diff --git a/spec/support/factories.cr b/spec/support/factories.cr
index af800bcb..c15da9fe 100644
--- a/spec/support/factories.cr
+++ b/spec/support/factories.cr
@@ -80,6 +80,78 @@ def checkout_git_branch(project, branch)
   end
 end
 
+def create_hg_repository(project, *versions)
+  Dir.cd(tmp_path) do
+    run "hg init #{Process.quote(project)}"
+  end
+
+  Dir.mkdir(File.join(hg_path(project), "src"))
+  File.write(File.join(hg_path(project), "src", "#{project}.cr"), "module #{project.capitalize}\nend")
+
+  Dir.cd(hg_path(project)) do
+    run "hg add #{Process.quote("src/#{project}.cr")}"
+  end
+
+  versions.each { |version| create_hg_release project, version }
+end
+
+def create_fork_hg_repository(project, upstream)
+  Dir.cd(tmp_path) do
+    run "hg clone #{Process.quote(hg_url(upstream))} #{Process.quote(project)}"
+  end
+end
+
+def create_hg_version_commit(project, version, shard : Bool | NamedTuple = true)
+  Dir.cd(hg_path(project)) do
+    if shard
+      contents = shard.is_a?(NamedTuple) ? shard : nil
+      create_shard project, version, contents
+    end
+    Dir.cd(hg_path(project)) do
+      name = shard[:name]? if shard.is_a?(NamedTuple)
+      name ||= project
+      File.touch "src/#{name}.cr"
+      run "hg add #{Process.quote("src/#{name}.cr")}"
+    end
+    create_hg_commit project, "release: v#{version}"
+  end
+end
+
+def create_hg_release(project, version, shard : Bool | NamedTuple = true)
+  create_hg_version_commit(project, version, shard)
+  create_hg_tag(project, "v#{version}")
+end
+
+def create_hg_tag(project, version)
+  Dir.cd(hg_path(project)) do
+    run "hg tag #{Process.quote(version)}"
+  end
+end
+
+def create_hg_commit(project, message = "new commit")
+  Dir.cd(hg_path(project)) do
+    run "hg commit -A -m #{Process.quote(message)}"
+  end
+end
+
+def checkout_new_hg_bookmark(project, branch)
+  Dir.cd(hg_path(project)) do
+    run "hg bookmark #{Process.quote(branch)}"
+  end
+end
+
+def checkout_new_hg_branch(project, branch)
+  Dir.cd(hg_path(project)) do
+    run "hg branch #{Process.quote(branch)}"
+  end
+end
+
+def checkout_hg_rev(project, rev)
+  Dir.cd(hg_path(project)) do
+    run "hg update -C #{Process.quote(rev)}"
+  end
+end
+
 def create_shard(project, version, contents : NamedTuple? = nil)
   spec = {name: project, version: version, crystal: Shards.crystal_version}
   spec = spec.merge(contents) if contents
@@ -116,6 +188,20 @@ def git_path(project)
   File.join(tmp_path, project.to_s)
 end
 
+def hg_commits(project, rev = ".")
+  Dir.cd(hg_path(project)) do
+    run("hg log --template='{node}\n' -r #{Process.quote(rev)}").strip.split('\n')
+  end
+end
+
+def hg_url(project)
+  "file://#{Path[hg_path(project)].to_posix}"
+end
+
+def hg_path(project)
+  File.join(tmp_path, project.to_s)
+end
+
 def rel_path(project)
   "../../spec/.repositories/#{project}"
 end
diff --git a/spec/support/requirement.cr b/spec/support/requirement.cr
index 7a7a8223..24594575 100644
--- a/spec/support/requirement.cr
+++ b/spec/support/requirement.cr
@@ -6,6 +6,10 @@ def commit(sha1)
   Shards::GitCommitRef.new(sha1)
 end
 
+def hg_branch(name)
+  Shards::HgBranchRef.new(name)
+end
+
 def version(version)
   Shards::Version.new(version)
 end
diff --git a/spec/unit/hg_resolver_spec.cr b/spec/unit/hg_resolver_spec.cr
new file mode 100644
index 00000000..66b99821
--- /dev/null
+++ b/spec/unit/hg_resolver_spec.cr
@@ -0,0 +1,153 @@
+require "./spec_helper"
+
+private def resolver(name)
+  Shards::HgResolver.new(name, hg_url(name))
+end
+
+module Shards
+  # Allow overriding `source` for the specs
+  class HgResolver
+    def source=(@source)
+    end
+  end
+
+  describe HgResolver do
+    before_each do
+      create_hg_repository "empty"
+      create_hg_commit "empty", "initial release"
+
+      create_hg_repository "unreleased"
+      create_hg_version_commit "unreleased", "0.1.0"
+      checkout_new_hg_branch "unreleased", "branch"
+      create_hg_commit "unreleased", "testing"
+      checkout_hg_rev "unreleased", "default"
+
+      create_hg_repository "library", "0.0.1", "0.1.0", "0.1.1", "0.1.2", "0.2.0"
+
+      # Create a version tag not prefixed by 'v' which should be ignored
+      create_hg_tag "library", "99.9.9"
+    end
+
+    it "available releases" do
+      resolver("empty").available_releases.should be_empty
+      resolver("library").available_releases.should eq(versions ["0.0.1", "0.1.0", "0.1.1", "0.1.2", "0.2.0"])
+    end
+
+    it "latest version for ref" do
+      expect_raises(Shards::Error, "No shard.yml was found for shard \"empty\" at commit #{hg_commits(:empty)[0]}") do
+        resolver("empty").latest_version_for_ref(hg_branch "default")
+      end
+      expect_raises(Shards::Error, "No shard.yml was found for shard \"empty\" at commit #{hg_commits(:empty)[0]}") do
+        resolver("empty").latest_version_for_ref(nil)
+      end
+      resolver("unreleased").latest_version_for_ref(hg_branch "default").should eq(version "0.1.0+hg.commit.#{hg_commits(:unreleased)[0]}")
+      resolver("unreleased").latest_version_for_ref(hg_branch "branch").should eq(version "0.1.0+hg.commit.#{hg_commits(:unreleased, "branch")[0]}")
+      resolver("unreleased").latest_version_for_ref(nil).should eq(version "0.1.0+hg.commit.#{hg_commits(:unreleased)[0]}")
+      resolver("library").latest_version_for_ref(hg_branch "default").should eq(version "0.2.0+hg.commit.#{hg_commits(:library)[0]}")
+      resolver("library").latest_version_for_ref(nil).should eq(version "0.2.0+hg.commit.#{hg_commits(:library)[0]}")
+      expect_raises(Shards::Error, "Could not find branch foo for shard \"library\" in the repository #{hg_url(:library)}") do
+        resolver("library").latest_version_for_ref(hg_branch "foo")
+      end
+    end
+
+    it "versions for" do
+      expect_raises(Shards::Error, "No shard.yml was found for shard \"empty\" at commit #{hg_commits(:empty)[0]}") do
+        resolver("empty").versions_for(Any)
+      end
+      resolver("library").versions_for(Any).should eq(versions ["0.0.1", "0.1.0", "0.1.1", "0.1.2", "0.2.0"])
+      resolver("library").versions_for(VersionReq.new "~> 0.1.0").should eq(versions ["0.1.0", "0.1.1", "0.1.2"])
+      resolver("library").versions_for(hg_branch "default").should eq(versions ["0.2.0+hg.commit.#{hg_commits(:library)[0]}"])
+      resolver("unreleased").versions_for(hg_branch "default").should eq(versions ["0.1.0+hg.commit.#{hg_commits(:unreleased)[0]}"])
+      resolver("unreleased").versions_for(Any).should eq(versions ["0.1.0+hg.commit.#{hg_commits(:unreleased)[0]}"])
+    end
+
+    it "read spec for release" do
+      spec = resolver("library").spec(version "0.1.1")
+      spec.original_version.should eq(version "0.1.1")
+      spec.version.should eq(version "0.1.1")
+    end
+
+    it "read spec for commit" do
+      version = version("0.2.0+hg.commit.#{hg_commits(:library)[0]}")
+      spec = resolver("library").spec(version)
+      spec.original_version.should eq(version "0.2.0")
+      spec.version.should eq(version)
+    end
+
+    it "install" do
+      library = resolver("library")
+
+      library.install_sources(version("0.1.2"), install_path("library"))
+      File.exists?(install_path("library", "src/library.cr")).should be_true
+      File.exists?(install_path("library", "shard.yml")).should be_true
+      Spec.from_file(install_path("library", "shard.yml")).version.should eq(version "0.1.2")
+
+      library.install_sources(version("0.2.0"), install_path("library"))
+      Spec.from_file(install_path("library", "shard.yml")).version.should eq(version "0.2.0")
+    end
+
+    it "install commit" do
+      library = resolver("library")
+      version = version "0.2.0+hg.commit.#{hg_commits(:library)[0]}"
+      library.install_sources(version, install_path("library"))
+      Spec.from_file(install_path("library", "shard.yml")).version.should eq(version "0.2.0")
+    end
+
+    it "origin changed" do
+      library = HgResolver.new("library", hg_url("library"))
+      library.install_sources(version("0.1.2"), install_path("library"))
+
+      # Change the origin in the cache repo to https://foss.heptapod.net/foo/bar
+      hgrc_path = File.join(library.local_path, ".hg", "hgrc")
+      hgrc = File.read(hgrc_path)
+      hgrc = hgrc.gsub(/(default\s*=\s*)([^\r\n]*)/, "\\1https://foss.heptapod.net/foo/bar")
+      File.write(hgrc_path, hgrc)
+      #
+      # All of these alternatives should not trigger origin as changed
+      same_origins = [
+        "https://foss.heptapod.net/foo/bar",
+        "https://foss.heptapod.net:1234/foo/bar",
+        "http://foss.heptapod.net/foo/bar",
+        "ssh://foss.heptapod.net/foo/bar",
+        "hg://foss.heptapod.net/foo/bar",
+        "rsync://foss.heptapod.net/foo/bar",
+        "hg@foss.heptapod.net:foo/bar",
+        "bob@foss.heptapod.net:foo/bar",
+        "foss.heptapod.net:foo/bar",
+      ]
+
+      same_origins.each do |origin|
+        library.source = origin
+        library.origin_changed?.should be_false
+      end
+
+      # These alternatives should all trigger origin as changed
+      changed_origins = [
+        "https://foss.heptapod.net/foo/bar2",
+        "https://foss.heptapod.net/foos/bar",
+        "https://hghubz.com/foo/bar",
+        "file:///foss.heptapod.net/foo/bar",
+        "hg@foss.heptapod.net:foo/bar2",
+        "hg@foss.heptapod2.net.com:foo/bar",
+        "",
+      ]
+
+      changed_origins.each do |origin|
+        library.source = origin
+        library.origin_changed?.should be_true
+      end
+    end
+
+    it "renders report version" do
+      resolver("library").report_version(version "1.2.3").should eq("1.2.3")
+      resolver("library").report_version(version "1.2.3+hg.commit.654875c9dbfa8d72fba70d65fd548d51ffb85aff").should eq("1.2.3 at 654875c")
+    end
+
+    it "#matches_ref" do
+      resolver = HgResolver.new("", "")
+      resolver.matches_ref?(HgCommitRef.new("1234567890abcdef"), Shards::Version.new("0.1.0.+hg.commit.1234567")).should be_true
+      resolver.matches_ref?(HgCommitRef.new("1234567890abcdef"), Shards::Version.new("0.1.0.+hg.commit.1234567890abcdef")).should be_true
+      resolver.matches_ref?(HgCommitRef.new("1234567"), Shards::Version.new("0.1.0.+hg.commit.1234567890abcdef")).should be_true
+    end
+  end
+end

From 976260c9219af479c5b7bc3c8da2be0d90cb3a9e Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Sat, 2 Jan 2021 22:40:34 +0100
Subject: [PATCH 03/22] Add some specs for mercurial bookmarks

---
 spec/support/factories.cr     |  1 +
 spec/support/requirement.cr   |  4 ++++
 spec/unit/hg_resolver_spec.cr | 11 +++++++++++
 3 files changed, 16 insertions(+)

diff --git a/spec/support/factories.cr b/spec/support/factories.cr
index c15da9fe..2766d014 100644
--- a/spec/support/factories.cr
+++ b/spec/support/factories.cr
@@ -130,6 +130,7 @@ end
 
 def create_hg_commit(project, message = "new commit")
   Dir.cd(hg_path(project)) do
+    File.write("src/#{project}.cr", "# #{message}", mode: "a")
     run "hg commit -A -m #{Process.quote(message)}"
   end
 end
diff --git a/spec/support/requirement.cr b/spec/support/requirement.cr
index 24594575..e308dbde 100644
--- a/spec/support/requirement.cr
+++ b/spec/support/requirement.cr
@@ -6,6 +6,10 @@ def commit(sha1)
   Shards::GitCommitRef.new(sha1)
 end
 
+def hg_bookmark(name)
+  Shards::HgBookmarkRef.new(name)
+end
+
 def hg_branch(name)
   Shards::HgBranchRef.new(name)
 end
diff --git a/spec/unit/hg_resolver_spec.cr b/spec/unit/hg_resolver_spec.cr
index 66b99821..97df5ef5 100644
--- a/spec/unit/hg_resolver_spec.cr
+++ b/spec/unit/hg_resolver_spec.cr
@@ -22,6 +22,12 @@ module Shards
       create_hg_commit "unreleased", "testing"
       checkout_hg_rev "unreleased", "default"
 
+      create_hg_repository "unreleased-bm"
+      create_hg_version_commit "unreleased-bm", "0.1.0"
+      checkout_new_hg_bookmark "unreleased-bm", "branch"
+      create_hg_commit "unreleased-bm", "testing"
+      checkout_hg_rev "unreleased-bm", "default"
+
       create_hg_repository "library", "0.0.1", "0.1.0", "0.1.1", "0.1.2", "0.2.0"
 
       # Create a version tag not prefixed by 'v' which should be ignored
@@ -43,6 +49,9 @@ module Shards
       resolver("unreleased").latest_version_for_ref(hg_branch "default").should eq(version "0.1.0+hg.commit.#{hg_commits(:unreleased)[0]}")
       resolver("unreleased").latest_version_for_ref(hg_branch "branch").should eq(version "0.1.0+hg.commit.#{hg_commits(:unreleased, "branch")[0]}")
       resolver("unreleased").latest_version_for_ref(nil).should eq(version "0.1.0+hg.commit.#{hg_commits(:unreleased)[0]}")
+      resolver("unreleased-bm").latest_version_for_ref(hg_branch "default").should eq(version "0.1.0+hg.commit.#{hg_commits("unreleased-bm")[0]}")
+      resolver("unreleased-bm").latest_version_for_ref(hg_bookmark "branch").should eq(version "0.1.0+hg.commit.#{hg_commits("unreleased-bm", "branch")[0]}")
+      resolver("unreleased-bm").latest_version_for_ref(nil).should eq(version "0.1.0+hg.commit.#{hg_commits("unreleased-bm")[0]}")
       resolver("library").latest_version_for_ref(hg_branch "default").should eq(version "0.2.0+hg.commit.#{hg_commits(:library)[0]}")
       resolver("library").latest_version_for_ref(nil).should eq(version "0.2.0+hg.commit.#{hg_commits(:library)[0]}")
       expect_raises(Shards::Error, "Could not find branch foo for shard \"library\" in the repository #{hg_url(:library)}") do
@@ -59,6 +68,8 @@ module Shards
       resolver("library").versions_for(hg_branch "default").should eq(versions ["0.2.0+hg.commit.#{hg_commits(:library)[0]}"])
       resolver("unreleased").versions_for(hg_branch "default").should eq(versions ["0.1.0+hg.commit.#{hg_commits(:unreleased)[0]}"])
       resolver("unreleased").versions_for(Any).should eq(versions ["0.1.0+hg.commit.#{hg_commits(:unreleased)[0]}"])
+      resolver("unreleased-bm").versions_for(hg_branch "default").should eq(versions ["0.1.0+hg.commit.#{hg_commits("unreleased-bm")[0]}"])
+      resolver("unreleased-bm").versions_for(Any).should eq(versions ["0.1.0+hg.commit.#{hg_commits("unreleased-bm")[0]}"])
     end
 
     it "read spec for release" do

From efdeda70859cf9ae733c1930ee499ce7c969ae8d Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Sun, 3 Jan 2021 10:45:07 +0100
Subject: [PATCH 04/22] HgResolver uses the Mercurial command server

---
 src/resolvers/hg.cr | 147 ++++++++++++++++++++++++++++++++++++--------
 1 file changed, 122 insertions(+), 25 deletions(-)

diff --git a/src/resolvers/hg.cr b/src/resolvers/hg.cr
index 8e35e94d..fdc45a70 100644
--- a/src/resolvers/hg.cr
+++ b/src/resolvers/hg.cr
@@ -110,6 +110,7 @@ module Shards
   class HgResolver < Resolver
     @@has_hg_command : Bool?
     @@hg_version : String?
+    @@hg_process : Process | Bool | Nil
 
     @origin_url : String?
 
@@ -134,7 +135,7 @@ module Shards
     end
 
     protected def self.hg_version
-      @@hg_version ||= `hg --version`[/\(version\s+([^)]*)\)/, 1]
+      @@hg_version ||= hg("--version")[/\(version\s+([^)]*)\)/, 1]
     end
 
     def read_spec(version : Version) : String?
@@ -142,7 +143,7 @@ module Shards
       ref = hg_ref(version)
 
       if file_exists?(ref, SPEC_FILENAME)
-        capture("hg cat -r #{Process.quote(ref.to_hg_ref)} #{Process.quote(SPEC_FILENAME)}")
+        capture_hg("cat", "-r", ref.to_hg_ref, SPEC_FILENAME)
       else
         Log.debug { "Missing \"#{SPEC_FILENAME}\" for #{name.inspect} at #{ref}" }
         nil
@@ -153,7 +154,7 @@ module Shards
       update_local_cache
       begin
         if file_exists?(ref, SPEC_FILENAME)
-          spec_yaml = capture("hg cat -r #{Process.quote(ref.to_hg_ref)} #{Process.quote(SPEC_FILENAME)}")
+          spec_yaml = capture_hg("cat", "-r", ref.to_hg_ref, SPEC_FILENAME)
           Spec.from_yaml(spec_yaml)
         end
       rescue Error
@@ -201,7 +202,7 @@ module Shards
     end
 
     protected def versions_from_tags
-      capture("hg tags --template '{tag}\\n'")
+      capture_hg("tags", "--template", "{tag}\\n")
         .split('\n')
         .sort!
         .compact_map { |tag| Version.new($1) if tag =~ VERSION_TAG }
@@ -209,13 +210,13 @@ module Shards
 
     def matches?(commit)
       if branch = dependency["branch"]?
-        !capture("hg log -r 'branch(#{tag}) and descendants(#{commit})' --template '{branch}\\n'").strip.empty?
+        !capture_hg("log", "-r", "branch(#{tag}) and descendants(#{commit})", "--template", "{branch}\\n").strip.empty?
       elsif bookmark = dependency["bookmark"]?
-        !capture("hg log -r 'bookmark(#{bookmark}) and descendants(#{commit})' --template '{bookmarks}\\n'").strip.empty?
+        !capture_hg("hg", "log", "-r", "bookmark(#{bookmark}) and descendants(#{commit})", "--template", "{bookmarks}\\n").strip.empty?
       elsif tag = dependency["tag"]?
-        !capture("hg log -r 'tag(#{tag}) and descendants(#{commit})' --template '{tags}\n'").strip.empty?
+        !capture_hg("hg", "log", "-r", "tag(#{tag}) and descendants(#{commit})", "--template", "{tags}\n").strip.empty?
       else
-        !capture("hg log -r #{commit}").strip.empty?
+        !capture_hg("log", "-r", commit).strip.empty?
       end
     end
 
@@ -224,12 +225,11 @@ module Shards
       ref = hg_ref(version)
 
       FileUtils.rm_r(install_path) if File.exists?(install_path)
-      Dir.mkdir_p(install_path)
-      run "hg clone --quiet -u #{Process.quote(ref.to_hg_ref(true))} -- #{Process.quote(local_path)} #{Process.quote(install_path)}"
+      run_hg "clone", "--quiet", "-u", ref.to_hg_ref(true), local_path, install_path, path: nil
     end
 
     def commit_sha1_at(ref : HgRef)
-      capture("hg log -r #{Process.quote(ref.to_hg_ref)} --template '{node}'").strip
+      capture_hg("log", "-r", ref.to_hg_ref, "--template", "{node}").strip
     end
 
     def local_path
@@ -326,13 +326,13 @@ module Shards
         #
         # An alternative would be to use the `@` bookmark, but only as long
         # as nothing new is committed.
-        run_in_current_folder "hg clone --quiet -- #{Process.quote(hg_url)} #{Process.quote(local_path)}"
+        run_hg "clone", hg_url, local_path, path: nil
       end
     end
 
     private def fetch_repository
       hg_retry(err: "Failed to update #{hg_url}") do
-        run "hg pull"
+        run_hg "pull"
       end
     end
 
@@ -366,7 +366,7 @@ module Shards
     end
 
     private def origin_url
-      @origin_url ||= capture("hg paths default").strip
+      @origin_url ||= capture_hg("paths", "default").strip
     end
 
     # Returns whether origin URLs have differing hosts and/or paths.
@@ -407,34 +407,131 @@ module Shards
     end
 
     private def file_exists?(ref : HgRef, path)
-      files = capture("hg files -r #{Process.quote(ref.to_hg_ref)} -- #{Process.quote(path)}")
+      files = capture_hg("files", "-r", ref.to_hg_ref, path)
       !files.strip.empty?
     end
 
-    private def capture(command, path = local_path)
-      run(command, capture: true, path: path).not_nil!
+    private def capture_hg(*args, path = local_path)
+      run_hg(*args, capture: true, path: path).not_nil!
     end
 
-    private def run(command, path = local_path, capture = false)
-      if Shards.local? && !Dir.exists?(path)
+    private def run_hg(*args, path = local_path, capture = false)
+      if path && Shards.local? && !Dir.exists?(path)
         dependency_name = File.basename(path)
         raise Error.new("Missing repository cache for #{dependency_name.inspect}. Please run without --local to fetch it.")
       end
-      Dir.cd(path) do
-        run_in_current_folder(command, capture)
+      HgResolver.hg(*args, path: path, capture: capture)
+    end
+
+    # Execute a hg command in the given path
+    #
+    # The command is run through the hg command server (if available) and
+    # the command line tool otherwise. The command server is started if the
+    # function is called for the first time.
+    def self.hg(*args, path = Dir.current, capture = true)
+      unless process = @@hg_process
+        Log.debug { "Start Mercurial command server" }
+
+        process = Process.new("hg",
+          ["serve", "--cmdserver", "pipe"],
+          env: {"HGENCODING" => "UTF-8"}, # enforce UTF-8 encoding
+          shell: true,
+          input: Process::Redirect::Pipe,
+          output: Process::Redirect::Pipe,
+          error: Process::Redirect::Inherit)
+        @@hg_process = process
+
+        output = process.output
+        # Read the hello block
+        channel = output.read_byte
+        len = output.read_bytes(UInt32, IO::ByteFormat::BigEndian)
+        hello = output.read_string(len)
+
+        Log.debug { "Mercurial command server hello: #{hello}" }
+
+        # Verify that the command server uses UTF-8 encoding
+        if encoding = hello.each_line.map(&.split(": ")).find(&.[0].== "encoding")
+          if encoding[1] != "UTF-8"
+            # actually, this should *never* happen
+            Log.warn { "Mercurial command server does not use UTF-8 encoding (#{encoding[1]}), fallback to direct command" }
+            @@hg_process = true
+          end
+        end
+      end
+
+      # Do not use the command server but run the command directly
+      if process.is_a?(Bool)
+        if path
+          return Dir.cd(path) { run_in_current_folder(*args, capture: capture) }
+        else
+          return run_in_current_folder(*args, capture: capture)
+        end
+      end
+
+      # Use the command server
+      cmd = String.build do |b|
+        # Run the command in the specified directory
+        b << "--cwd" << "\0" << path << "\0" if path
+        b << args.each.join("\0")
+      end
+
+      input = process.input
+      output = process.output
+
+      input.write("runcommand\n".to_slice)
+      input.write_bytes(cmd.bytesize, IO::ByteFormat::BigEndian)
+      input.write(cmd.to_slice)
+
+      result = capture ? String::Builder.new : nil
+      error_msg = ""
+      status = 0
+      while true
+        channel = output.read_byte
+        len = output.read_bytes(UInt32, IO::ByteFormat::BigEndian)
+
+        case channel
+        when 'o'
+          if result
+            result << output.read_string(len)
+          else
+            output.read_string(len)
+          end
+        when 'e'
+          error_msg = output.read_string(len)
+        when 'r'
+          status = output.read_bytes(Int32)
+          break
+        when 'L'
+          raise Error.new("Mercurial process expects a line input")
+        when 'I'
+          raise Error.new("Mercurial process expects a block input")
+        end
+      end
+
+      if status.zero?
+        result.to_s if result
+      else
+        str = error_msg.to_s
+        if str.starts_with?("abort: ") && (idx = str.index('\n'))
+          message = str[7...idx]
+        else
+          message = str
+        end
+        raise Error.new("Failed hg #{args.join(" ")} (#{message}). Maybe a commit, branch, bookmark or file doesn't exist?")
       end
     end
 
-    private def run_in_current_folder(command, capture = false)
+    # Run the hg command line tool with some command line args in the current folder
+    private def self.run_in_current_folder(*args, capture = false)
       unless HgResolver.has_hg_command?
         raise Error.new("Error missing hg command line tool. Please install Mercurial first!")
       end
 
-      Log.debug { command }
+      Log.debug { "hg #{args.join(" ")}" }
 
       output = capture ? IO::Memory.new : Process::Redirect::Close
       error = IO::Memory.new
-      status = Process.run(command, shell: true, output: output, error: error)
+      status = Process.run("hg", args, shell: true, output: output, error: error)
 
       if status.success?
         output.to_s if capture
@@ -445,7 +542,7 @@ module Shards
         else
           message = str
         end
-        raise Error.new("Failed #{command} (#{message}). Maybe a commit, branch, bookmark or file doesn't exist?")
+        raise Error.new("Failed hg #{args.join(" ")} (#{message}). Maybe a commit, branch or file doesn't exist?")
       end
     end
 

From 3da7e526e0e88235c06e835e35aa0eb33605d555 Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Sun, 3 Jan 2021 10:14:40 +0100
Subject: [PATCH 05/22] Specs for HgResolver use the command server

---
 spec/support/factories.cr | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/spec/support/factories.cr b/spec/support/factories.cr
index 2766d014..8f1f222b 100644
--- a/spec/support/factories.cr
+++ b/spec/support/factories.cr
@@ -82,14 +82,14 @@ end
 
 def create_hg_repository(project, *versions)
   Dir.cd(tmp_path) do
-    run "hg init #{Process.quote(project)}"
+    Shards::HgResolver.hg "init", project
   end
 
   Dir.mkdir(File.join(hg_path(project), "src"))
   File.write(File.join(hg_path(project), "src", "#{project}.cr"), "module #{project.capitalize}\nend")
 
   Dir.cd(hg_path(project)) do
-    run "hg add #{Process.quote("src/#{project}.cr")}"
+    Shards::HgResolver.hg "add", "src/#{project}.cr"
   end
 
   versions.each { |version| create_hg_release project, version }
@@ -97,7 +97,7 @@ end
 
 def create_fork_hg_repository(project, upstream)
   Dir.cd(tmp_path) do
-    run "hg clone #{Process.quote(hg_url(upstream))} #{Process.quote(project)}"
+    Shards::HgResolver.hg "clone", hg_url(upstream), project
   end
 end
 
@@ -111,7 +111,7 @@ def create_hg_version_commit(project, version, shard : Bool | NamedTuple = true)
       name = shard[:name]? if shard.is_a?(NamedTuple)
       name ||= project
       File.touch "src/#{name}.cr"
-      run "hg add #{Process.quote("src/#{name}.cr")}"
+      Shards::HgResolver.hg "add", "src/#{name}.cr"
     end
     create_hg_commit project, "release: v#{version}"
   end
@@ -124,32 +124,32 @@ end
 
 def create_hg_tag(project, version)
   Dir.cd(hg_path(project)) do
-    run "hg tag #{Process.quote(version)}"
+    Shards::HgResolver.hg "tag", version
   end
 end
 
 def create_hg_commit(project, message = "new commit")
   Dir.cd(hg_path(project)) do
     File.write("src/#{project}.cr", "# #{message}", mode: "a")
-    run "hg commit -A -m #{Process.quote(message)}"
+    Shards::HgResolver.hg "commit", "-A", "-m", message
   end
 end
 
 def checkout_new_hg_bookmark(project, branch)
   Dir.cd(hg_path(project)) do
-    run "hg bookmark #{Process.quote(branch)}"
+    Shards::HgResolver.hg "bookmark", branch
   end
 end
 
 def checkout_new_hg_branch(project, branch)
   Dir.cd(hg_path(project)) do
-    run "hg branch #{Process.quote(branch)}"
+    Shards::HgResolver.hg "branch", branch
   end
 end
 
 def checkout_hg_rev(project, rev)
   Dir.cd(hg_path(project)) do
-    run "hg update -C #{Process.quote(rev)}"
+    Shards::HgResolver.hg "update", "-C", rev
   end
 end
 
@@ -191,7 +191,7 @@ end
 
 def hg_commits(project, rev = ".")
   Dir.cd(hg_path(project)) do
-    run("hg log --template='{node}\n' -r #{Process.quote(rev)}").strip.split('\n')
+    Shards::HgResolver.hg("log", "--template", "{node}\n", "-r", rev).not_nil!.strip.split('\n')
   end
 end
 

From 8b4fd1a260872819aa4d245f49639805adcf85e7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Johannes=20M=C3=BCller?= <straightshoota@gmail.com>
Date: Sun, 3 Jan 2021 15:50:13 +0100
Subject: [PATCH 06/22] [CI] Install mercurial

---
 .circleci/config.yml | 10 ++++++++--
 .travis.yml          |  1 +
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/.circleci/config.yml b/.circleci/config.yml
index 0ac1bc4e..be0d5ae2 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -40,6 +40,9 @@ jobs:
     docker:
       - image: crystallang/crystal:latest
     steps:
+      - run:
+          name: Install mercurial
+          command: apt-get update && apt-get install mercurial -y
       - shards-make-test
 
   test-on-osx:
@@ -49,14 +52,17 @@ jobs:
       - with-brew-cache:
           steps:
             - run:
-                name: Install Crystal
-                command: brew install crystal
+                name: Install Crystal and Mercurial
+                command: brew install crystal mercurial
       - shards-make-test
 
   test-on-nightly:
     docker:
       - image: crystallang/crystal:nightly
     steps:
+      - run:
+          name: Install mercurial
+          command: apt-get update && apt-get install mercurial -y
       - shards-make-test
 
 workflows:
diff --git a/.travis.yml b/.travis.yml
index 45f5a148..039a7409 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,5 +10,6 @@ before_script: |
   git config --global column.ui always
 
 script:
+  - apt-get update && apt-get install mercurial -y
   - make test
   - crystal tool format --check src spec

From d32e82a6302103eac1aa1215593432a9e1920a12 Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Sun, 3 Jan 2021 16:11:06 +0100
Subject: [PATCH 07/22] Forward error message in `hg_retry`

---
 src/resolvers/hg.cr | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/resolvers/hg.cr b/src/resolvers/hg.cr
index 8e35e94d..513c1414 100644
--- a/src/resolvers/hg.cr
+++ b/src/resolvers/hg.cr
@@ -341,10 +341,10 @@ module Shards
       loop do
         yield
         break
-      rescue Error
+      rescue ex : Error
         retries += 1
         next if retries < 3
-        raise Error.new(err)
+        raise Error.new("#{err}: #{ex}")
       end
     end
 

From 736b656deebcc378b387f69a6723c4331a2be094 Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Sun, 3 Jan 2021 16:24:56 +0100
Subject: [PATCH 08/22] Ensure parent directory exists before hg clone

---
 src/resolvers/hg.cr | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/resolvers/hg.cr b/src/resolvers/hg.cr
index 513c1414..1a73a091 100644
--- a/src/resolvers/hg.cr
+++ b/src/resolvers/hg.cr
@@ -321,12 +321,14 @@ module Shards
     end
 
     private def mirror_repository
+      path = local_path
+      Dir.mkdir_p(File.dirname(path))
       hg_retry(err: "Failed to clone #{hg_url}") do
         # We checkout the working directory so that "." is meaningful.
         #
         # An alternative would be to use the `@` bookmark, but only as long
         # as nothing new is committed.
-        run_in_current_folder "hg clone --quiet -- #{Process.quote(hg_url)} #{Process.quote(local_path)}"
+        run_in_current_folder "hg clone --quiet -- #{Process.quote(hg_url)} #{Process.quote(path)}"
       end
     end
 

From fa972636a6be2899d0564bd20fa37500639c3490 Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Sun, 3 Jan 2021 16:49:13 +0100
Subject: [PATCH 09/22] Ensure target path exists when installing sources from
 hg

---
 src/resolvers/hg.cr | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/resolvers/hg.cr b/src/resolvers/hg.cr
index ab6e0236..78c07623 100644
--- a/src/resolvers/hg.cr
+++ b/src/resolvers/hg.cr
@@ -225,6 +225,7 @@ module Shards
       ref = hg_ref(version)
 
       FileUtils.rm_r(install_path) if File.exists?(install_path)
+      Dir.mkdir_p(install_path)
       run_hg "clone", "--quiet", "-u", ref.to_hg_ref(true), local_path, install_path, path: nil
     end
 

From 16da02b480f8653f62816f1bb54baf657fa0817d Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Sun, 3 Jan 2021 18:31:21 +0100
Subject: [PATCH 10/22] Remove install path before installing sources from hg

---
 src/resolvers/hg.cr | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/resolvers/hg.cr b/src/resolvers/hg.cr
index 1a73a091..128f4253 100644
--- a/src/resolvers/hg.cr
+++ b/src/resolvers/hg.cr
@@ -322,7 +322,8 @@ module Shards
 
     private def mirror_repository
       path = local_path
-      Dir.mkdir_p(File.dirname(path))
+      FileUtils.rm_r(path) if File.exists?(path)
+      Dir.mkdir_p(path)
       hg_retry(err: "Failed to clone #{hg_url}") do
         # We checkout the working directory so that "." is meaningful.
         #

From 2cb5a69d2325642c3e9c01d82a0490728561c955 Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Mon, 4 Jan 2021 10:28:29 +0100
Subject: [PATCH 11/22] [CI] Fix installation of mercurial on travis-ci

---
 .travis.yml | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/.travis.yml b/.travis.yml
index 039a7409..6dc9bbd7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,6 +3,10 @@ language: crystal
 os:
   - linux
 
+before_install:
+  - sudo apt-get update
+  - sudo apt-get -y install mercurial
+
 before_script: |
   make
   git config --global user.email "you@example.com"
@@ -10,6 +14,5 @@ before_script: |
   git config --global column.ui always
 
 script:
-  - apt-get update && apt-get install mercurial -y
   - make test
   - crystal tool format --check src spec

From bd79e579931629d8c1c75136beca1b4194ce3001 Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Mon, 4 Jan 2021 11:14:56 +0100
Subject: [PATCH 12/22] [CI] Install mercurial in github workflow

---
 .github/workflows/ci.yml | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index af1061cc..233940fc 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -26,6 +26,15 @@ jobs:
           git config --global column.ui always
           git config --global core.autocrlf false
 
+      - name: Install Python
+        uses: actions/setup-python@v2
+
+      - name: Upgrade pip
+        run: python -m pip install --upgrade pip
+
+      - name: Install Mercurial
+        run: pip install mercurial
+
       - name: Install Crystal
         uses: oprypin/install-crystal@v1
         with:

From 06b9255f184e59e4404f42c0fa7a988661ec16c0 Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Mon, 4 Jan 2021 11:28:28 +0100
Subject: [PATCH 13/22] Call `Process` with full quoted command line

Otherwise it won't work on Windows currently.
---
 src/resolvers/hg.cr | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/resolvers/hg.cr b/src/resolvers/hg.cr
index 53c84883..4634fcd9 100644
--- a/src/resolvers/hg.cr
+++ b/src/resolvers/hg.cr
@@ -436,8 +436,7 @@ module Shards
       unless process = @@hg_process
         Log.debug { "Start Mercurial command server" }
 
-        process = Process.new("hg",
-          ["serve", "--cmdserver", "pipe"],
+        process = Process.new("hg serve --cmdserver pipe",
           env: {"HGENCODING" => "UTF-8"}, # enforce UTF-8 encoding
           shell: true,
           input: Process::Redirect::Pipe,
@@ -535,7 +534,8 @@ module Shards
 
       output = capture ? IO::Memory.new : Process::Redirect::Close
       error = IO::Memory.new
-      status = Process.run("hg", args, shell: true, output: output, error: error)
+      command = "hg #{args.each.map { |arg| Process.quote(arg) }.join(" ")}"
+      status = Process.run(command, shell: true, output: output, error: error)
 
       if status.success?
         output.to_s if capture
@@ -546,7 +546,7 @@ module Shards
         else
           message = str
         end
-        raise Error.new("Failed hg #{args.join(" ")} (#{message}). Maybe a commit, branch or file doesn't exist?")
+        raise Error.new("Failed #{command} (#{message}). Maybe a commit, branch or file doesn't exist?")
       end
     end
 

From d9e2a7b99f57a79a36d1ce5aec55dc21e1c1af91 Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Mon, 4 Jan 2021 12:29:40 +0100
Subject: [PATCH 14/22] Quote shell arguments correctly

---
 spec/support/factories.cr |  2 +-
 src/resolvers/hg.cr       | 15 ++++++++-------
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/spec/support/factories.cr b/spec/support/factories.cr
index 2766d014..d32b48b0 100644
--- a/spec/support/factories.cr
+++ b/spec/support/factories.cr
@@ -191,7 +191,7 @@ end
 
 def hg_commits(project, rev = ".")
   Dir.cd(hg_path(project)) do
-    run("hg log --template='{node}\n' -r #{Process.quote(rev)}").strip.split('\n')
+    run("hg log --template=#{Process.quote("{node}\n")} -r #{Process.quote(rev)}").strip.split('\n')
   end
 end
 
diff --git a/src/resolvers/hg.cr b/src/resolvers/hg.cr
index 128f4253..2997babb 100644
--- a/src/resolvers/hg.cr
+++ b/src/resolvers/hg.cr
@@ -201,7 +201,7 @@ module Shards
     end
 
     protected def versions_from_tags
-      capture("hg tags --template '{tag}\\n'")
+      capture("hg tags --template #{Process.quote("{tag}\n")}")
         .split('\n')
         .sort!
         .compact_map { |tag| Version.new($1) if tag =~ VERSION_TAG }
@@ -209,14 +209,15 @@ module Shards
 
     def matches?(commit)
       if branch = dependency["branch"]?
-        !capture("hg log -r 'branch(#{tag}) and descendants(#{commit})' --template '{branch}\\n'").strip.empty?
+        rev = "branch(\"#{tag}\") and descendants(#{commit})"
       elsif bookmark = dependency["bookmark"]?
-        !capture("hg log -r 'bookmark(#{bookmark}) and descendants(#{commit})' --template '{bookmarks}\\n'").strip.empty?
+        rev = "bookmark(\"#{bookmark}\") and descendants(#{commit})"
       elsif tag = dependency["tag"]?
-        !capture("hg log -r 'tag(#{tag}) and descendants(#{commit})' --template '{tags}\n'").strip.empty?
+        rev = "tag(\"tag\") and descendants(#{commit})"
       else
-        !capture("hg log -r #{commit}").strip.empty?
+        rev = commit
       end
+      !capture("hg log -r #{Process.quote(rev)}").strip.empty?
     end
 
     def install_sources(version : Version, install_path : String)
@@ -229,7 +230,7 @@ module Shards
     end
 
     def commit_sha1_at(ref : HgRef)
-      capture("hg log -r #{Process.quote(ref.to_hg_ref)} --template '{node}'").strip
+      capture("hg log -r #{Process.quote(ref.to_hg_ref)} --template #{Process.quote("{node}\n")}").strip
     end
 
     def local_path
@@ -352,7 +353,7 @@ module Shards
     end
 
     private def delete_repository
-      Log.debug { "rm -rf #{Process.quote(local_path)}'" }
+      Log.debug { "rm -rf #{Process.quote(local_path)}" }
       Shards::Helpers.rm_rf(local_path)
       @origin_url = nil
     end

From dbac5f9860a55cb425d5bd544070ebcd5c266aa3 Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Mon, 4 Jan 2021 11:45:28 +0100
Subject: [PATCH 15/22] Remove a `file://` prefix from urls on Windows

---
 src/resolvers/hg.cr | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/resolvers/hg.cr b/src/resolvers/hg.cr
index 2997babb..93b6adbf 100644
--- a/src/resolvers/hg.cr
+++ b/src/resolvers/hg.cr
@@ -325,12 +325,18 @@ module Shards
       path = local_path
       FileUtils.rm_r(path) if File.exists?(path)
       Dir.mkdir_p(path)
-      hg_retry(err: "Failed to clone #{hg_url}") do
+
+      source = hg_url
+      # Remove a "file://" from the beginning, otherwise the path might be invalid
+      # on Windows.
+      source = source[7..] if source.starts_with?("file://")
+
+      hg_retry(err: "Failed to clone #{source}") do
         # We checkout the working directory so that "." is meaningful.
         #
         # An alternative would be to use the `@` bookmark, but only as long
         # as nothing new is committed.
-        run_in_current_folder "hg clone --quiet -- #{Process.quote(hg_url)} #{Process.quote(path)}"
+        run_in_current_folder "hg clone --quiet -- #{Process.quote(source)} #{Process.quote(path)}"
       end
     end
 

From 16099f841ea7a7921d16301e5f2028b574c53277 Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Mon, 4 Jan 2021 12:14:45 +0100
Subject: [PATCH 16/22] Set explicit username for hg commit and hg tag

---
 spec/support/factories.cr | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/spec/support/factories.cr b/spec/support/factories.cr
index d32b48b0..7cad5926 100644
--- a/spec/support/factories.cr
+++ b/spec/support/factories.cr
@@ -124,14 +124,14 @@ end
 
 def create_hg_tag(project, version)
   Dir.cd(hg_path(project)) do
-    run "hg tag #{Process.quote(version)}"
+    run "hg tag -u #{Process.quote("Your Name <you@example.com>")} #{Process.quote(version)}"
   end
 end
 
 def create_hg_commit(project, message = "new commit")
   Dir.cd(hg_path(project)) do
     File.write("src/#{project}.cr", "# #{message}", mode: "a")
-    run "hg commit -A -m #{Process.quote(message)}"
+    run "hg commit -u #{Process.quote("Your Name <you@example.com>")} -A -m #{Process.quote(message)}"
   end
 end
 

From a4a2e92009635a1ede8555e10758836f7ebfc2c8 Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Mon, 4 Jan 2021 19:33:32 +0100
Subject: [PATCH 17/22] Only check for existence of `.hg/dirstate` for
 identifying hg repos

---
 src/resolvers/hg.cr | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/src/resolvers/hg.cr b/src/resolvers/hg.cr
index 93b6adbf..86185a35 100644
--- a/src/resolvers/hg.cr
+++ b/src/resolvers/hg.cr
@@ -369,10 +369,7 @@ module Shards
     end
 
     private def valid_repository?
-      File.each_line(File.join(local_path, ".hg", "dirstate")) do |line|
-        return true if line =~ /mirror\s*=\s*true/
-      end
-      false
+      File.exists?(File.join(local_path, ".hg", "dirstate"))
     end
 
     private def origin_url

From 3266b2b2d07281a3ee0d4232ab6cc7a6a9f3c7ba Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Mon, 4 Jan 2021 19:34:18 +0100
Subject: [PATCH 18/22] Improve code of HgResolver

---
 src/resolvers/hg.cr | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/src/resolvers/hg.cr b/src/resolvers/hg.cr
index 86185a35..8abb75bc 100644
--- a/src/resolvers/hg.cr
+++ b/src/resolvers/hg.cr
@@ -202,7 +202,7 @@ module Shards
 
     protected def versions_from_tags
       capture("hg tags --template #{Process.quote("{tag}\n")}")
-        .split('\n')
+        .lines
         .sort!
         .compact_map { |tag| Version.new($1) if tag =~ VERSION_TAG }
     end
@@ -267,7 +267,6 @@ module Shards
           return HgTagRef.new value
         when "commit"
           return HgCommitRef.new value
-        else
         end
       end
 
@@ -329,7 +328,7 @@ module Shards
       source = hg_url
       # Remove a "file://" from the beginning, otherwise the path might be invalid
       # on Windows.
-      source = source[7..] if source.starts_with?("file://")
+      source = source.lchop("file://")
 
       hg_retry(err: "Failed to clone #{source}") do
         # We checkout the working directory so that "." is meaningful.
@@ -349,8 +348,7 @@ module Shards
     private def hg_retry(err = "Failed to update repository")
       retries = 0
       loop do
-        yield
-        break
+        return yield
       rescue ex : Error
         retries += 1
         next if retries < 3

From 7afdb5038268e692396891e9a3149dba0715329e Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Mon, 4 Jan 2021 20:25:12 +0100
Subject: [PATCH 19/22] Add `to_hg_revset` and `to_hg_ref` methods

---
 src/resolvers/hg.cr | 46 ++++++++++++++++++++++++++++++++-------------
 1 file changed, 33 insertions(+), 13 deletions(-)

diff --git a/src/resolvers/hg.cr b/src/resolvers/hg.cr
index 8abb75bc..bfa829ee 100644
--- a/src/resolvers/hg.cr
+++ b/src/resolvers/hg.cr
@@ -15,8 +15,12 @@ module Shards
     def initialize(@branch : String)
     end
 
-    def to_hg_ref(simple = false)
-      simple ? @branch : "branch(\"#{@branch}\") and head()"
+    def to_hg_ref
+      @branch
+    end
+
+    def to_hg_revset
+      "branch(\"#{@branch}\") and head()"
     end
 
     def to_s(io)
@@ -33,8 +37,12 @@ module Shards
     def initialize(@bookmark : String)
     end
 
-    def to_hg_ref(simple = false)
-      simple ? @bookmark : "bookmark(\"#{@bookmark}\")"
+    def to_hg_ref
+      @bookmark
+    end
+
+    def to_hg_revset
+      "bookmark(\"#{@bookmark}\")"
     end
 
     def to_s(io)
@@ -51,8 +59,12 @@ module Shards
     def initialize(@tag : String)
     end
 
-    def to_hg_ref(simple = false)
-      simple ? @tag : "tag(\"#{@tag}\")"
+    def to_hg_ref
+      @tag
+    end
+
+    def to_hg_revset
+      "tag(\"#{@tag}\")"
     end
 
     def to_s(io)
@@ -75,7 +87,11 @@ module Shards
       commit.starts_with?(other.commit) || other.commit.starts_with?(commit)
     end
 
-    def to_hg_ref(simple = false)
+    def to_hg_ref
+      @commit
+    end
+
+    def to_hg_revset
       @commit
     end
 
@@ -94,7 +110,11 @@ module Shards
   end
 
   struct HgCurrentRef < HgRef
-    def to_hg_ref(simple = false)
+    def to_hg_revset
+      "."
+    end
+
+    def to_hg_ref
       "."
     end
 
@@ -142,7 +162,7 @@ module Shards
       ref = hg_ref(version)
 
       if file_exists?(ref, SPEC_FILENAME)
-        capture("hg cat -r #{Process.quote(ref.to_hg_ref)} #{Process.quote(SPEC_FILENAME)}")
+        capture("hg cat -r #{Process.quote(ref.to_hg_revset)} #{Process.quote(SPEC_FILENAME)}")
       else
         Log.debug { "Missing \"#{SPEC_FILENAME}\" for #{name.inspect} at #{ref}" }
         nil
@@ -153,7 +173,7 @@ module Shards
       update_local_cache
       begin
         if file_exists?(ref, SPEC_FILENAME)
-          spec_yaml = capture("hg cat -r #{Process.quote(ref.to_hg_ref)} #{Process.quote(SPEC_FILENAME)}")
+          spec_yaml = capture("hg cat -r #{Process.quote(ref.to_hg_revset)} #{Process.quote(SPEC_FILENAME)}")
           Spec.from_yaml(spec_yaml)
         end
       rescue Error
@@ -226,11 +246,11 @@ module Shards
 
       FileUtils.rm_r(install_path) if File.exists?(install_path)
       Dir.mkdir_p(install_path)
-      run "hg clone --quiet -u #{Process.quote(ref.to_hg_ref(true))} -- #{Process.quote(local_path)} #{Process.quote(install_path)}"
+      run "hg clone --quiet -u #{Process.quote(ref.to_hg_ref)} -- #{Process.quote(local_path)} #{Process.quote(install_path)}"
     end
 
     def commit_sha1_at(ref : HgRef)
-      capture("hg log -r #{Process.quote(ref.to_hg_ref)} --template #{Process.quote("{node}\n")}").strip
+      capture("hg log -r #{Process.quote(ref.to_hg_revset)} --template #{Process.quote("{node}\n")}").strip
     end
 
     def local_path
@@ -412,7 +432,7 @@ module Shards
     end
 
     private def file_exists?(ref : HgRef, path)
-      files = capture("hg files -r #{Process.quote(ref.to_hg_ref)} -- #{Process.quote(path)}")
+      files = capture("hg files -r #{Process.quote(ref.to_hg_revset)} -- #{Process.quote(path)}")
       !files.strip.empty?
     end
 

From 1453032e815c566a94d8568e267dd5b0efffac8a Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Tue, 5 Jan 2021 21:27:23 +0100
Subject: [PATCH 20/22] Remove unused method `HgResolver#matches?`

---
 src/resolvers/hg.cr | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/src/resolvers/hg.cr b/src/resolvers/hg.cr
index bfa829ee..4528307d 100644
--- a/src/resolvers/hg.cr
+++ b/src/resolvers/hg.cr
@@ -227,19 +227,6 @@ module Shards
         .compact_map { |tag| Version.new($1) if tag =~ VERSION_TAG }
     end
 
-    def matches?(commit)
-      if branch = dependency["branch"]?
-        rev = "branch(\"#{tag}\") and descendants(#{commit})"
-      elsif bookmark = dependency["bookmark"]?
-        rev = "bookmark(\"#{bookmark}\") and descendants(#{commit})"
-      elsif tag = dependency["tag"]?
-        rev = "tag(\"tag\") and descendants(#{commit})"
-      else
-        rev = commit
-      end
-      !capture("hg log -r #{Process.quote(rev)}").strip.empty?
-    end
-
     def install_sources(version : Version, install_path : String)
       update_local_cache
       ref = hg_ref(version)

From fff4ccc531c8a26eadfcee36e4700cb890ca9c5a Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Tue, 5 Jan 2021 23:22:37 +0100
Subject: [PATCH 21/22] HgResolver#file_exists? does not use exceptions if the
 file does not exist

Exceptions should only be used on real errors, not on expected fails.
---
 src/resolvers/hg.cr | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/src/resolvers/hg.cr b/src/resolvers/hg.cr
index 4528307d..8887db80 100644
--- a/src/resolvers/hg.cr
+++ b/src/resolvers/hg.cr
@@ -419,25 +419,24 @@ module Shards
     end
 
     private def file_exists?(ref : HgRef, path)
-      files = capture("hg files -r #{Process.quote(ref.to_hg_revset)} -- #{Process.quote(path)}")
-      !files.strip.empty?
+      run("hg files -r #{Process.quote(ref.to_hg_revset)} -- #{Process.quote(path)}", raise_on_fail: false)
     end
 
     private def capture(command, path = local_path)
-      run(command, capture: true, path: path).not_nil!
+      run(command, capture: true, path: path).as(String)
     end
 
-    private def run(command, path = local_path, capture = false)
+    private def run(command, path = local_path, capture = false, raise_on_fail = true)
       if Shards.local? && !Dir.exists?(path)
         dependency_name = File.basename(path)
         raise Error.new("Missing repository cache for #{dependency_name.inspect}. Please run without --local to fetch it.")
       end
       Dir.cd(path) do
-        run_in_current_folder(command, capture)
+        run_in_current_folder(command, capture, raise_on_fail: raise_on_fail)
       end
     end
 
-    private def run_in_current_folder(command, capture = false)
+    private def run_in_current_folder(command, capture = false, raise_on_fail = true)
       unless HgResolver.has_hg_command?
         raise Error.new("Error missing hg command line tool. Please install Mercurial first!")
       end
@@ -449,8 +448,12 @@ module Shards
       status = Process.run(command, shell: true, output: output, error: error)
 
       if status.success?
-        output.to_s if capture
-      else
+        if capture
+          output.to_s
+        else
+          true
+        end
+      elsif raise_on_fail
         str = error.to_s
         if str.starts_with?("abort: ") && (idx = str.index('\n'))
           message = str[7...idx]

From 2e31e09d4f05bb62419aeefc1718100bafafd8c5 Mon Sep 17 00:00:00 2001
From: Frank Fischer <frank-fischer@shadow-soft.de>
Date: Wed, 6 Jan 2021 15:40:14 +0100
Subject: [PATCH 22/22] Add documentation for hg to SPEC.md

---
 SPEC.md | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/SPEC.md b/SPEC.md
index a39de50c..1ac9b0fe 100644
--- a/SPEC.md
+++ b/SPEC.md
@@ -244,17 +244,36 @@ installations, you must use the generic `git` resolver.
 
 Example: `gitlab: thelonlyghost/minitest.cr`
 
+#### hg
+
+A Mercurial repository URL (String).
+
+The URL may be any protocol supported by Mercurial, which includes SSH and HTTPS.
+
+The Merurial repository will be cloned, the list of versions (and associated
+`shard.yml`) will be extracted from Mercurial tags (e.g., `v1.2.3`).
+
+One of the other attributes (`version`, `tag`, `branch`, `bookmark` or `commit`) is
+required. When missing, Shards will install the `@` bookmark or `tip`.
+
+Example: `hg: https://hg.example.org/crystal-library`
+
+
 #### commit
 
-Install a Git dependency at the specified commit (String).
+Install a Git or Mercurial dependency at the specified commit (String).
 
 #### tag
 
-Install a Git dependency at the specified tag (String).
+Install a Git or Mercurial dependency at the specified tag (String).
 
 #### branch
 
-Install a Git dependency at the specified branch (String).
+Install a Git dependency at the specified branch or a Mercurial dependency at the specified named branch (String).
+
+#### bookmark
+
+Install a Mercurial dependency at the specified bookmark (String).
 
 ### development_dependencies