Add justfile

Add a `just` config file with various useful commands. Note that a bunch
of these commands do not succeed currently on master, specifically:

- just lint
- just docsrs
- just sane

Will fix as separate PRs

Author: tcharding

justfile

@@ -0,0 +1,39 @@
+default:
+  @just --list
+
+# Cargo build everything.
+build:
+  cargo build --all-targets --all-features
+
+# Cargo check everything.
+check:
+  cargo check --all-targets --all-features
+
+# Lint everything.
+lint:
+  cargo +nightly clippy --all-targets --all-features -- --deny warnings
+
+# Run the formatter.
+fmt:
+  cargo +nightly fmt
+
+# Check the formatting.
+fmt-check:
+  cargo +nightly fmt --check
+
+# Run the benchmark suite.
+bench:
+  RUSTFLAGS='--cfg=bench' cargo +nightly bench
+
+# Build the docs (same as for docs.rs).
+docsrs:
+  RUSTDOCFLAGS="--cfg docsrs" cargo +nightly rustdoc --all-features -- -D rustdoc::broken-intra-doc-links
+
+# Quick and dirty CI useful for pre-push checks.
+sane: fmt-check lint
+  cargo test --quiet --all-targets --no-default-features > /dev/null || exit 1
+  cargo test --quiet --all-targets > /dev/null || exit 1
+  cargo test --quiet --all-targets --all-features > /dev/null || exit 1
+
+  # doctests don't get run from workspace root with `cargo test`.
+  cargo test --quiet --doc || exit 1