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Mix checks the lock of every Git dependency on every command, which spawned git twice per dependency (~19ms on macOS). The revision is now read from a detached .git/HEAD and the origin from a plain url under [remote "origin"] in .git/config, which is the state Mix leaves checkouts in. Each falls back to git independently for anything else (symbolic HEAD, includes, worktree config, GIT_CONFIG* environment variables, quotes, escapes, comments, line continuations, several urls). Closes elixir-lang#16040
josevalim
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Oct 31, 2026
josevalim
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Thank you, some comments inline! I am afraid we should probably only read the HEAD instead.
| defp read_rev(git_dir) do | ||
| with {:ok, head} <- File.read(Path.join(git_dir, "HEAD")), | ||
| rev = String.trim_trailing(head), | ||
| true <- rev =~ ~r/\A([0-9a-f]{40}|[0-9a-f]{64})\z/ do |
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Why do we need this validation? Can it ever be a non-valid ref?
| end | ||
| end | ||
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| defp read_origin(git_dir) do |
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Hrm, there is too much going on in here and I feel we are going to have more pitfalls. If we can't easily get the URL, then I am afraid we will need to use the git CLI indeed.
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Closes #16040.
Mix.SCM.Git.lock_status/1spawned git twice per Git dependency on every Mix command (~19ms per dependency on macOS). Now the revision is read from a detached.git/HEAD, and the origin from a plainurlunder[remote "origin"]in.git/config. That is the state Mix leaves its checkouts in.Each value falls back to git on its own for anything else, so the answer never differs from git's. Fallback cases: symbolic HEAD, includes,
config.worktree,GIT_CONFIG*environment variables, quotes, escapes, comments, line continuations, several urls.Checked against git 2.54 with a differential test covering ~80 config, HEAD and environment variants. The unusual configs are also part of the new tests, which compare
lock_status/1againstgit config remote.origin.url.Phoenix app with git dependencies on phoenix and phoenix_live_view:
lock_status/1goes from 19ms to 85µs per dependency.