Error with git: remote HEAD is ambiguous, may be one of the following

Question

After branching and pushing to the remote, a git remote show origin gives the report

HEAD branch (remote HEAD is ambiguous, may be one of the following):  
    master  
    otherbranch  

What does the imply?

It is a critical error?

remote origin
  Fetch URL: [email protected]:/home/gituser/repos/csfsconf.git
  Push  URL: [email protected]:/home/gituser/repos/csfsconf.git
  HEAD branch (remote HEAD is ambiguous, may be one of the following):
    master
    otherbranch

Answer 1

The thread at http://forums.wf.klevo.sk/comments.php?DiscussionID=155 has a discussion of this topic. In particular the thread mentions:

# make a new branch where you can make and commit changes to
$git checkout -b darth-kool
Switched to a new branch 'darth-kool'

# * marks current branch
$git branch -l
* darth-kool
master

Perhaps you need to mark your current branch? If not, the rest of the thread may help.

Answer 2

You can see the same warning in this blog post

(master)jj@im-jj:~/demo$ git checkout -b rc-1.0
Switched to a new branch 'rc-1.0'
(rc-1.0)jj@im-jj:~/demo$ git push origin rc-1.0
Total 0 (delta 0), reused 0 (delta 0)
To my-server:/git/demo.git
 * [new branch]      rc-1.0 -> rc-1.0
(rc-1.0)jj@im-jj:~/demo$ git remote show origin 
* remote origin
  URL: my-server:/git/demo.git
  HEAD branch (remote HEAD is ambiguous, may be one of the following):
    master
    rc-1.0
  Remote branches:
    master tracked
    rc-1.0 tracked
  Local branch configured for 'git pull':
    master merges with remote master
  Local refs configured for 'git push':
    master pushes to master (up to date)
    rc-1.0 pushes to rc-1.0 (up to date)

That (pushing a new current branch) will introduce a new HEAD reference to the remote repo.

If you look at the Git sources for this warning message, it tries to get the remote HEAD names through get_head_names() which calls :

matches = guess_remote_head(find_ref_by_name(remote_refs, "HEAD"),
+                   fetch_map, 1);

As described in this patch:

Determining HEAD is ambiguous since it is done by comparing SHA1s.

(see the code here)

In the case of multiple matches we return refs/heads/master if it matches, else we return the first match we encounter. builtin-remote needs all matches returned to it, so add a flag for it to request such.