completion: zsh: stop leaking local cache variable

From: "D. Ben Knoble" <[email protected]>

Completing commands like "git rebase" in one repository will leak the local __git_repo_path into the shell's environment so that completing commands after changing to a different repository will give the old repository's references (or none at all).

The bug report on the mailing list [1] suggests one simple way to observe this yourself:

Enter the following commands from some directory:
mkdir a b b/c
for d (a b); git -C $d init && git -C $d commit --allow-empty -m init cd a
git branch foo
pushd ../b/c
git branch bar

Now type these:
git rebase <TAB>… # completion for bar available; C-c to abort declare -p __git_repo_path # outputs /path/to/b/.git popd
git branch # outputs foo, main
git rebase <TAB>… # completion candidates are bar, main!

Ideally, the last typed <TAB> should be yielding foo, main.

Commit beb6ee7163 (completion: extract repository discovery from __gitdir(), 2017-02-03) anticipated this problem by marking __git_repo_path as local in __git_main and __gitk_main for Bash completion but did not give the same mark to _git for Zsh completion. Thus make __git_repo_path local for Zsh completion, too.

[1]: https://lore.kernel.org/git/CALnO6CBv3+e2WL6n6Mh7ZZHCX2Ni8GpvM4a-bQYxNqjmgZdwdg@mail.gmail.com/

---
completion: zsh: stop leaking local cache variable

Prevent leaking a local variable used to cache the repo path, which breaks future completions in different repositories using the shell, when using contributed Zsh completion.

------------------------------------------------------------------------

I made a few attempts at starting a test script for this based on
https://unix.stackexchange.com/a/668827/301073, but that code doesn't work and it was all becoming precariously complicated (sh starting zsh to start zsh in a pty which would receive keystrokes and check specific
outputs: I couldn't make certain pieces work in a normal way locally, let alone as part of Git's test suite). Suffice to say I have tested this myself?

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1725%2Fbenknoble%2Ffix-zsh-completion-repo-cache-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1725/benknoble/fix-zsh-completion-repo-cache-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1725

 contrib/completion/git-completion.zsh | 1 +
 1 file changed, 1 insertion(+)

index cac6f618817..f5877bd7a1e 100644
@@ -272,6 +272,7 @@ _git ()
 {
 	local _ret=1
 	local cur cword prev
+	local __git_repo_path
 
 	cur=${words[CURRENT]}
 	prev=${words[CURRENT-1]}

base-commit: 786a3e4b8d754d2b14b1208b98eeb0a554ef19a8

gitgitgadget

Will queue. The explanation makes tons of sense.

Thanks.