The code called resolve_ref("HEAD") and stored the result in old.path to
record which branch it used to be on, so that it can say between which
branches the switch took place in the reflog.
However, lookup_commit_reference_gently() is called immediately after
old.path is initialized. This call can prime replace-object machinery
which in turn collects the loose refs, and calls resolve_ref() inside. As
the string returned from resolve_ref() is a static buffer that is local to
it, this ended up clobbering the value of old.path. The reflog either
recorded a wrong "switched from" branch (when the last call to resolve_ref
happens to be from the branch namespace), or recorded from a detached HEAD
(otherwise). Neither is correct.
Store the returned string away with xstrdup() to avoid this.
Signed-off-by: Junio C Hamano <gitster@xxxxxxxxx>
---
* This was present ever since checkout was rewritten in C at 782c2d6
(Build in checkout, 2008-02-07), but probably got a lot easier to
trigger recently due to the addition of object replacement code.
As it depends on the order readdir() in refs.c::get_ref_dir() returns
the entries, there is no universally reproducible test, but I found it
in real life inside my git.git primary working repository.
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 28cdc51..48de146 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -715,10 +715,12 @@ static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
unsigned char rev[20];
int flag;
memset(&old, 0, sizeof(old));
- old.path = resolve_ref("HEAD", rev, 0, &flag);
+ old.path = xstrdup(resolve_ref("HEAD", rev, 0, &flag));
old.commit = lookup_commit_reference_gently(rev, 1);
- if (!(flag & REF_ISSYMREF))
+ if (!(flag & REF_ISSYMREF)) {
+ free((char *)old.path);
old.path = NULL;
+ }
if (old.path && !prefixcmp(old.path, "refs/heads/"))
old.name = old.path + strlen("refs/heads/");
@@ -741,6 +743,7 @@ static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
update_refs_for_switch(opts, &old, new);
ret = post_checkout_hook(old.commit, new->commit, 1);
+ free((char *)old.path);
return ret || opts->writeout_error;
}
--
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