You can get the revision of a remote git repository by using the git ls-remote command
This simple example will output the revision for all branches and tags.
git ls-remote url-to-git-repo:username/repo.git
Output will look something like this:
8eef34582a... HEAD
4f4d5e18fd... refs/heads/master
84ae6b827a... refs/heads/another-branch
...
You can narrow the output down to just one branch by doing the following
git ls-remote url-to-git-repo:username/repo.git branch-name