Suggestion: better error reporting when setting HEAD

(Please CC me on your replies, thanks)

If you take any valid git repo and then do the following:

  git symbolic-ref HEAD master
  (instead of "git symbolic-ref HEAD refs/heads/master")

then other git commands (e.g. "git log") will return this error message:

  fatal: Not a git repository

I'd like to suggest two "usability" improvements:

1- changing the error message to explain why the directory is no longer
   considered a git repo. Maybe something along the lines of:

     fatal: Invalid reference in .git/HEAD

2- To prevent this error from happening in the first place, git-symbolic-ref
   could refuse to change HEAD to a non-existent ref.

Cheers, Francois