Question about git log --merge option

Dear list:

Just encountered the --merge option for git log.

In the man page, it has the following explanation:
- After a failed merge, show refs that touch files having a conflict
and don't exist on all heads to merge.

I tried this option and get below results:

1. For a failed merge (with conflicts), if the conflicted file does
not exist on either side of the merge, the --merge option will return
the log from the other side.

2. If the conflicted file exists on both sides of the merge, the
--merge option will return the latest change on either side. (i.e: git
log -1 -- conflict_file / git log -1 --merge -- conflict_file may
return different results, whichever changed the latest)

I'm not sure whether above behavior is the unexpected result (cannot find detailed explanation for --merge option online).

Thanks

Andrey Hsiao <andreyhsiao@gmail.com> writes:

	git log --merge [options] -- $paths

is roughly the same as

	git log [options] HEAD...MERGE_HEAD -- $paths'

where $paths' is $paths limited to those with conflicts. You can further think of that as a rough equivalent of

	git log [options] ^X HEAD MERGE_HEAD -- $paths'

where X is the merge base between the tips of these two branches:

    X---o---o---o---H
     \
      o---o---o---M

And the commits among these ('o's, H and M in the picture), the ones that change any of the $paths' are shown. If you further limit the output (e.g. with -n<n>, or --since=<time>), you may not see all of them, of course.

Thanks Junio, I understand the option's meaning now :)

On Thu, Apr 14, 2016 at 4:37 AM, Junio C Hamano <gitster@pobox.com> wrote: