When we lock a reference like "foo" we need to handle the case where
"foo" exists, but is an empty directory. That's what this code added
in bc7127ef0f (ref locking: allow 'foo' when 'foo/bar' used to exist
but not anymore., 2006-09-30) seems like it should be dealing with.
Except it doesn't, and we never take this branch. The reason is that
when bc7127ef0f was written this looked like:
ref = resolve_ref([...]);
if (!ref && errno == EISDIR) {
[...]
And in resolve_ref() we had this code:
fd = open(path, O_RDONLY);
if (fd < 0)
return NULL;
I.e. we would attempt to read "foo" with open(), which would fail with
EISDIR and we'd return NULL. We'd then take this branch, call
remove_empty_directories() and continue.
Since a1c1d8170d (refs_resolve_ref_unsafe: handle d/f conflicts for
writes, 2017-10-06) we don't. E.g. in the case of
files_copy_or_rename_ref() our callstack will look something like:
[...] ->
files_copy_or_rename_ref() ->
lock_ref_oid_basic() ->
refs_resolve_ref_unsafe()
At that point the first (now only) refs_resolve_ref_unsafe() call in
lock_ref_oid_basic() would do the equivalent of this in the resulting
call to refs_read_raw_ref() in refs_resolve_ref_unsafe():
/* Via refs_read_raw_ref() */
fd = open(path, O_RDONLY);
if (fd < 0)
/* get errno == EISDIR */
/* later, in refs_resolve_ref_unsafe() */
if ([...] && errno != EISDIR)
return NULL;
[...]
/* returns the refs/heads/foo to the caller, even though it's a directory */
return refname;
I.e. even though we got an "errno == EISDIR" we won't take this
branch, since in cases of EISDIR "resolved" is always
non-NULL. I.e. we pretend at this point as though everything's OK and
there is no "foo" directory.
We then proceed with the entire ref update and don't call
remove_empty_directories() until we call commit_ref_update(). See
5387c0d883 (commit_ref(): if there is an empty dir in the way, delete
it, 2016-05-05) for the addition of that code, and
a1c1d8170d (refs_resolve_ref_unsafe: handle d/f conflicts for writes,
2017-10-06) for the commit that changed the original codepath added in
bc7127ef0f to use this "EISDIR" handling.
Further historical commentary:
Before the two preceding commits the caller in files_reflog_expire()
was the only one out of our 4 callers that would pass non-NULL as an
oid. We would then set a (now gone) "resolve_flags" to
"RESOLVE_REF_READING" and just before that "errno != EISDIR" check do:
if (resolve_flags & RESOLVE_REF_READING)
return NULL;
There may have been some case where this ended up mattering and we
couldn't safely make this change before we removed the "oid"
parameter, but I don't think there was, see [1] for some discussion on
that.
In any case, now that we've removed the "oid" parameter in a preceding
commit we can be sure that this code is redundant, so let's remove it.
1. http://lore.kernel.org/git/871r801yp6.fsf@evledraar.gmail.com
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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