Taking into consideration that there are several git commands that make no sense in a bare repository (because bare repositories don't use indexes and do not have a working directory),
git reset --hard HEAD^
is not a solution to uncommit the last change in such a repository.
Searching through the Internet, all I could find related to the topic is this, in which I am presented three ways of doing this:
1. "update the ref manually (which involves plumbing)";
2. "git push -f from a non-bare repository";
3. "git branch -f this $that".
Which solution do yo think is more appropriate or what other ways are there to do this? Unfortunately, the documentation I found about git bare repositories is fairly poor.
You can use the git update-ref command. To remove the last commit, you would use:
$ git update-ref HEAD HEAD^
Or if you're not in the branch from which you cant to remove the last commit:
$ git update-ref refs/heads/branch-name branch-name^
You could also pass a sha1 if you want:
$ git update-ref refs/heads/branch-name a12d48e2
See the documentation of the git-update-ref command.