Git shouldn't allow to push a new branch called HEAD

Hi all,


following from a discussion in IRC freenode #git between me, sitaram an
shruggar


step to reproduce:

$ mkdir /tmp/gitbug
$ cd /tmp/gitbug/

$ # create a fake remote repo
$ git init --bare remote.git

$ # clone it with the user that will generate the bug
$ git clone remote.git buggenerator
$ cd buggenerator/
$ touch whatever
$ git add .
$ git commit -m "first commit"
$ git push origin master 

$ # now clone the same repo the other guy is the "victim" of this issue
$ cd ..
$ git clone remote.git victim

$ # time to create the remote HEAD branch
$ cd buggenerator/
$ git push origin HEAD:HEAD

$ # the remote refs has been created!
$ git ls-remote

$ # another commit
$ echo 'any change' >> whatever 
$ git commit -a -m "some change"
$ git push origin master 

$ # the refs/heads/HEAD is still where it was
$ git ls-remote

$ # now from the victim perspective
$ cd ../victim/

$ # every time executing a fetch he will get a force update
$ # or maybe even an error, seen it my real repo, don't know how
$ # to reproduce
$ git fetch 
$ git fetch 
$ git ls-remote
$ git fetch 
$ git ls-remote
$ git branch -a



full console log:

mastro@mastroc3 ~  $ mkdir /tmp/gitbug
mastro@mastroc3 ~  $ cd /tmp/gitbug/
mastro@mastroc3 /tmp/gitbug  $ git init --bare remote.git
Initialized empty Git repository in /tmp/gitbug/remote.git/
mastro@mastroc3 /tmp/gitbug  $ git clone remote.git buggenerator
Cloning into buggenerator...
done.
warning: You appear to have cloned an empty repository.
mastro@mastroc3 /tmp/gitbug  $ cd buggenerator/
mastro@mastroc3 /tmp/gitbug/buggenerator (master #) $ touch whatever
mastro@mastroc3 /tmp/gitbug/buggenerator (master #) $ git add .
mastro@mastroc3 /tmp/gitbug/buggenerator (master #) $ git commit -m
"first commit"
[master (root-commit) 11d0a12] first commit
 0 files changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 whatever
mastro@mastroc3 /tmp/gitbug/buggenerator (master) $ git push origin
master 
Counting objects: 3, done.
Writing objects: 100% (3/3), 213 bytes, done.
Total 3 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
To /tmp/gitbug/remote.git
 * [new branch]      master -> master
mastro@mastroc3 /tmp/gitbug/buggenerator (master) $ cd ..
mastro@mastroc3 /tmp/gitbug  $ git clone remote.git victim
Cloning into victim...
done.
mastro@mastroc3 /tmp/gitbug  $ cd buggenerator/

# now creating the HEAD remote branch

mastro@mastroc3 /tmp/gitbug/buggenerator (master) $ git push origin
HEAD:HEAD
Total 0 (delta 0), reused 0 (delta 0)
To /tmp/gitbug/remote.git
 * [new branch]      HEAD -> HEAD
mastro@mastroc3 /tmp/gitbug/buggenerator (master) $ git ls-remote
From /tmp/gitbug/remote.git
11d0a122125e50e78c7aa4aa81a3d6090dba648e	HEAD
11d0a122125e50e78c7aa4aa81a3d6090dba648e	refs/heads/HEAD <-----
shouldn't be there!
11d0a122125e50e78c7aa4aa81a3d6090dba648e	refs/heads/master
mastro@mastroc3 /tmp/gitbug/buggenerator (master) $ echo 'any change' >>
whatever 
mastro@mastroc3 /tmp/gitbug/buggenerator (master *) $ git commit -a -m
"some change"
[master 77852ef] some change
 1 files changed, 1 insertions(+), 0 deletions(-)
mastro@mastroc3 /tmp/gitbug/buggenerator (master) $ git push origin
master 
Counting objects: 5, done.
Writing objects: 100% (3/3), 253 bytes, done.
Total 3 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
To /tmp/gitbug/remote.git
   11d0a12..77852ef  master -> master
mastro@mastroc3 /tmp/gitbug/buggenerator (master) $ git ls-remote
From /tmp/gitbug/remote.git
77852effa972187d60d4c75145198991f1c0f868	HEAD
11d0a122125e50e78c7aa4aa81a3d6090dba648e	refs/heads/HEAD
77852effa972187d60d4c75145198991f1c0f868	refs/heads/master
mastro@mastroc3 /tmp/gitbug/buggenerator (master) $ cd ../victim/
mastro@mastroc3 /tmp/gitbug/victim (master) $ git fetch 
remote: Counting objects: 5, done.
remote: Total 3 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
From /tmp/gitbug/remote
   11d0a12..77852ef  master     -> origin/master
mastro@mastroc3 /tmp/gitbug/victim (master) $ git fetch 
From /tmp/gitbug/remote
 + 77852ef...11d0a12 HEAD       -> origin/HEAD  (forced update)
mastro@mastroc3 /tmp/gitbug/victim (master) $ git fetch 
From /tmp/gitbug/remote
   11d0a12..77852ef  master     -> origin/master
mastro@mastroc3 /tmp/gitbug/victim (master) $ git ls-remote
From /tmp/gitbug/remote.git
77852effa972187d60d4c75145198991f1c0f868	HEAD
11d0a122125e50e78c7aa4aa81a3d6090dba648e	refs/heads/HEAD
77852effa972187d60d4c75145198991f1c0f868	refs/heads/master
mastro@mastroc3 /tmp/gitbug/victim (master) $ git fetch 
From /tmp/gitbug/remote
 + 77852ef...11d0a12 HEAD       -> origin/HEAD  (forced update)
mastro@mastroc3 /tmp/gitbug/victim (master) $ git ls-remote
From /tmp/gitbug/remote.git
77852effa972187d60d4c75145198991f1c0f868	HEAD
11d0a122125e50e78c7aa4aa81a3d6090dba648e	refs/heads/HEAD
77852effa972187d60d4c75145198991f1c0f868	refs/heads/master
mastro@mastroc3 /tmp/gitbug/victim (master) $ git branch -a
* master
  remotes/origin/HEAD -> origin/master
  remotes/origin/master




this can be fixed with:

git push --delete origin HEAD
(or git push origin :HEAD)

then
git remote prune origin



But I think that git shouldn't allow the remote HEAD reference to be
created in the first place

regards,
Daniele