fix(install): read prompt from /dev/tty when stdin is piped (#42)

* fix(install): read prompt from /dev/tty when stdin is piped

When the install script is run via the documented `curl ... | sh`
pattern, stdin is the pipe carrying script bytes, so `read -r response`
cannot capture keystrokes and the service-install prompt silently
ignores keyboard input (reported by Ivvor on Matrix).

A previous fix (eff317ae, Dec 2025) addressed this with `< /dev/tty`,
but PRs #36 / #37 resynced this file from freenet-core and dropped the
override. Reapply the fix and harden it for environments without a
controlling terminal.

The new logic:
- If stdin is a TTY, read normally (covers `sh install.sh`).
- Else, probe /dev/tty by actually opening it (`{ true </dev/tty; }`)
  rather than relying on `[ -r /dev/tty ]`, which can return true even
  when the open later fails. If /dev/tty is openable, read from it
  (covers `curl | sh`).
- Otherwise, skip the prompt rather than aborting under `set -eu`
  (covers truly non-interactive shells, e.g. CI or `setsid`).

Verified via a pty harness: `curl | sh` simulation under `script(1)`
reads "y" from /dev/tty and proceeds; `setsid ... </dev/null` skips
the prompt and prints follow-up instructions.

Note: freenet-core/scripts/install.sh has the identical bug; a matching
fix will follow there to keep the resync in sync.

[AI-assisted - Claude]

* fix(install): address review feedback - $0 detection, EOF guard

Five-perspective review on PR #42 surfaced three issues with the
initial fix:

- Codex P2: discriminating only on `[ -t 0 ]` regresses
  `printf 'y' | sh install.sh` automation patterns. When stdin is
  piped but the script ran from a file, the user's answer is on
  stdin, not /dev/tty.

- Skeptical #1: `read -r response` returning EOF (Ctrl-D, closed
  stdin) under `set -eu` aborts the script.

- Skeptical #10: comment used an em-dash, which Ian's writing-style
  rule rejects.

Redesigned the dispatch around `$0`: when sh runs a script file
(file-execution), $0 is the script path; when sh reads its own
source from stdin (`curl | sh`), $0 is the shell name. The case
arm tests for known shell names and only redirects to /dev/tty in
that branch. The file-execution arm reads from stdin as before, so
piped automation still works.

Both `read` calls now have `|| response=""` so EOF leaves the
default-N case path intact rather than aborting.

Also (lower priority feedback applied):

- Skipped path now mentions FREENET_NO_SERVICE=1 as the documented
  way to bypass the prompt non-interactively (Skeptical #2/#3).

- Removed the redundant "Non-interactive shell detected" info line
  (Skeptical #7); the existing `*)` case arm already prints
  "Skipping service installation" plus remediation guidance.

- Added a NOTE block at the top of the file pointing future
  resync agents at the freenet-core sibling and explaining why
  the prompt block must not be flattened back to a plain `read`
  (Big-picture #5).

Re-tested via the same pty harness across five scenarios:
  1. `curl | sh` under pty: reads 'y' from /dev/tty, installs.
  2. `sh install.sh` interactive: reads from stdin.
  3. `printf 'y' | sh install.sh`: reads from piped stdin (regression
     test for Codex's concern).
  4. `setsid ... </dev/null`: skips, prints FREENET_NO_SERVICE hint.
  5. `sh install.sh </dev/null`: handles EOF without aborting.

All five pass.

[AI-assisted - Claude]

Author: sanity

hugo-site/static/install.sh

@@ -9,6 +9,14 @@
 #   FREENET_INSTALL_DIR  - Installation directory (default: ~/.local/bin)
 #   FREENET_NO_SERVICE   - Set to 1 to skip service installation prompt
 #   FREENET_VERSION      - Specific version to install (default: latest)
+#
+# NOTE: A near-identical copy lives at freenet-core/scripts/install.sh.
+# Keep the two in sync. In particular, the service-install prompt
+# (look for "Would you like to install Freenet as a system service")
+# MUST keep its $0 + /dev/tty handling so that `curl | sh` users can
+# answer the prompt - see freenet/web PR #42 / freenet-core PR for
+# context. A previous fix was already lost once via a bulk resync
+# (web PRs #36/#37).
 
 set -eu
 
@@ -409,11 +417,45 @@ main() {
         print_path_instructions "$install_dir"
     fi
 
-    # Ask about service installation (unless FREENET_NO_SERVICE is set)
+    # Ask about service installation (unless FREENET_NO_SERVICE is set).
+    #
+    # When the script is piped via `curl ... | sh`, sh reads its own script
+    # source from stdin. A plain `read` at this point would consume bytes
+    # of script source instead of capturing the user's answer, so we
+    # redirect from /dev/tty in that case.
+    #
+    # We detect "sh is reading the script from stdin" via $0: when sh runs
+    # a script file, $0 is the script path; when sh reads its source from
+    # stdin, $0 is the shell name itself (e.g. "sh", "bash"). In the
+    # script-file case we read from stdin as before, so existing
+    # automation patterns like `printf 'y\n' | sh install.sh` still work.
+    # The robust way to bypass the prompt in any invocation form is
+    # FREENET_NO_SERVICE=1.
+    #
+    # `{ true </dev/tty; } 2>/dev/null` is used instead of `[ -r /dev/tty ]`:
+    # the access check can succeed even when the process has no
+    # controlling terminal and the subsequent open(2) fails with ENXIO.
+    # Probe by actually opening /dev/tty.
+    #
+    # `read -r response || response=""` keeps EOF (e.g. Ctrl-D, closed
+    # stdin) from aborting the script under `set -eu`.
     if [ "${FREENET_NO_SERVICE:-0}" != "1" ]; then
         echo ""
-        printf "Would you like to install Freenet as a system service? [y/N] "
-        read -r response
+        response=""
+        case "${0##*/}" in
+            sh|bash|dash|ash|busybox|-sh|-bash|-dash|-ash)
+                # Script source is on stdin (`curl | sh` form).
+                if { true </dev/tty; } 2>/dev/null; then
+                    printf "Would you like to install Freenet as a system service? [y/N] "
+                    read -r response </dev/tty || response=""
+                fi
+                ;;
+            *)
+                # Script ran as a file; stdin carries the user's answer.
+                printf "Would you like to install Freenet as a system service? [y/N] "
+                read -r response || response=""
+                ;;
+        esac
         case "$response" in
             [yY]|[yY][eE][sS])
                 info "Installing service..."
@@ -427,6 +469,8 @@ main() {
                 echo ""
                 echo "You can install the service later with:"
                 echo "  freenet service install"
+                echo ""
+                echo "To skip this prompt entirely in scripted installs, set FREENET_NO_SERVICE=1."
                 ;;
         esac
     fi