[PATCH] fetch: limit shared symref check only for local branches

From: Orgad Shaneh via GitGitGadget <gitgitgadget@gmail.com>
Date: May 16, 2022, 08:37 UTC
Message-ID: <pull.1266.git.git.1652690275625.gitgitgadget@gmail.com>

From: Orgad Shaneh <orgads@gmail.com>

This check was introduced in 8ee5d73137f (Fix fetch/pull when run without --update-head-ok, 2008-10-13) in order to protect against replacing the ref of the active branch by mistake, for example by running git fetch origin master:master.

It was later extended in 8bc1f39f411 (fetch: protect branches checked out in all worktrees, 2021-12-01) to scan all worktrees.

This operation is very expensive (takes about 30s in my repository) when there are many tags or branches, and it is executed on every fetch, even if no local heads are updated at all.

Limit it to protect only refs/heads/* to improve fetch performance.

Signed-off-by: Orgad Shaneh <orgads@gmail.com>
---
    fetch: limit shared symref check only for local branches

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1266%2Forgads%2Ffetch-perf-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1266/orgads/fetch-perf-v1
Pull-Request: https://github.com/git/git/pull/1266

 builtin/fetch.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/builtin/fetch.c b/builtin/fetch.c
index e3791f09ed5..4f16fc357b0 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -1440,6 +1440,7 @@ static void check_not_current_branch(struct ref *ref_map,
 	const struct worktree *wt;
 	for (; ref_map; ref_map = ref_map->next)
 		if (ref_map->peer_ref &&
+			starts_with(ref_map->peer_ref->name, "refs/heads/") &&
 		    (wt = find_shared_symref(worktrees, "HEAD",
 					     ref_map->peer_ref->name)) &&
 		    !wt->is_bare)

base-commit: 277cf0bc36094f6dc4297d8c9cef79df045b735d

-- 
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