If HEAD doesn't point at anything during the initial check, then we
should make sure that it *still* doesn't point at anything when we are
ready to update the reference. Otherwise, another process might commit
while we are working (e.g., while we are waiting for the user to edit
the commit message) and we will silently overwrite it.
This fixes a failing test in t7516.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Committing involves the following steps:
1. Determine the current value of HEAD (if any).
2. Create the new commit object.
3. Update HEAD.
Please note that step 2 can take arbitrarily long, because it might
involve the user editing a commit message.
If a second process sneaks in a commit during step 2, then the first
commit process should fail. This is usually done correctly, because
step 3 verifies that HEAD still points at the same commit that it
pointed to during step 1.
However, if there is a race when creating an *orphan* commit, then the
test in step 3 is skipped.
Add tests for proper handling of such races. One of the new tests
fails. It will be fixed in a moment.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
