[PATCH 0/8] Fix some problems with reflog expiration

In addition to a few cleanups, this patch series fixes some problems that I noticed when working on mh/reflog-expire:

* Ignore '--updateref' when expiring the reflog of a symbolic
  reference, because the alternatives are all pretty silly. See the
  log message for commit 6/8 for more information.

* Ignore '--updateref' when *all* reflog entries are expired by "git
  reflog expire" or "git reflog delete". Currently, this sets the
  reference to 0{40}, which breaks the repository. (Another
  alternative would be to delete the reference in this situation, but
  that seemed too radical to me somehow.)

* When expiring the reflog for a symbolic reference, lock the symbolic
  reference rather than its referent.

This patch series applies on top of master merged together with sb/atomic-push, like the "refs-have-new" patch series that I just submitted. It is also available from my GitHub account [1] as branch "expire-updateref-fixes".

There is a minor conflict between this patch series and "mh/refs-have-new":

<<<<<<< HEAD
		if (!is_null_sha1(update->new_sha1)) {
			if (!update->lock->force_write &&
			    !hashcmp(update->lock->old_sha1, update->new_sha1)) {
				unlock_ref(update->lock);
				update->lock = NULL;
			} else if (write_ref_sha1(update->lock, update->new_sha1,
						  update->msg)) {
||||||| merged common ancestors
		if (!is_null_sha1(update->new_sha1)) {
			if (write_ref_sha1(update->lock, update->new_sha1,
					   update->msg)) {
=======
		if ((flags & REF_HAVE_NEW) && !is_null_sha1(update->new_sha1)) {
			if (write_ref_sha1(update->lock, update->new_sha1,
					   update->msg)) {

It can be resolved in the obvious way:

<<<<<<<
		if ((flags & REF_HAVE_NEW) && !is_null_sha1(update->new_sha1)) {
			if (!update->lock->force_write &&
			    !hashcmp(update->lock->old_sha1, update->new_sha1)) {
				unlock_ref(update->lock);
				update->lock = NULL;
			} else if (write_ref_sha1(update->lock, update->new_sha1,
						  update->msg)) {

By the way, both of these patch series conflict with sb/atomic-push-fix, which is in pu. My understanding is that Stefan wants to rework that patch series anyway, but if not I would be happy to show how to resolve the conflicts.

Michael

[1] https://github.com/mhagger/git

Michael Haggerty (8):
  write_ref_sha1(): remove check for lock == NULL
  write_ref_sha1(): Move write elision test to callers
  lock_ref_sha1_basic(): do not set force_write for missing references
  reflog: fix documentation
  reflog: rearrange the manpage
  reflog_expire(): ignore --updateref for symbolic references
  reflog_expire(): never update a reference to null_sha1
  reflog_expire(): lock symbolic refs themselves, not their referent

 Documentation/git-reflog.txt | 65 +++++++++++++++++++++++---------------------
 builtin/reflog.c             |  2 +-
 refs.c                       | 55 ++++++++++++++++++++-----------------
 3 files changed, 65 insertions(+), 57 deletions(-)