Syncing HEAD

[Christian Couder <christian.couder@gmail.com>]

Hi,

When cloning with --mirror, the clone gets its HEAD initialized with
the value HEAD has in its origin remote. After that if HEAD changes in
origin there is no simple way to sync HEAD at the same time as the
refs are synced.

It looks like the simplest way to sync HEAD is:

1) git remote show origin
2) parse "HEAD branch: XXX" from the output of the above command
3) git symbolic-ref HEAD refs/heads/XXX

It looks like it would be quite easy to add an option to `fetch` to
sync HEAD at the same time as regular refs are synced because every
fetch from an origin that uses a recent Git contains something like:

19:55:39.304976 pkt-line.c:80           packet:          git< YYYYYYYY
HEAD\0multi_ack thin-pack side-band side-band-64k ofs-delta shallow
deepen-since deepen-not deepen-relative no-progress include-tag
multi_ack_detailed no-done symref=HEAD:refs/heads/test-1
agent=git/2.18.0

which in this example shows that HEAD is a symref to refs/heads/test-1
in origin.

Is there a reason why no such option already exists? Would it makes
sense to add one? Is there any reason why it's not a good idea? Or am
I missing something?

I am asking because GitLab uses HEAD in the bare repos it manages to
store the default branch against which the Merge Requests (same thing
as Pull Requests on GitHub) are created.

So when people want to keep 2 GitLab hosted repos in sync, GitLab
needs to sync HEADs too, not just the refs.

I think this could be useful to other setups than GitLab though.

Thanks,
Christian.