Bug: lstrip in get_upstream_branch function

[rrao24]

There is a bug in the get_upstream_branch() function concerning the usage of lstrip() on line 1107

jupyterlab-git/jupyterlab_git/git.py

Line 1107 in 0e1e697

remote_branch = rev_parse_output.strip().lstrip(remote_name + "/")

Say that line 1106

jupyterlab-git/jupyterlab_git/git.py

Line 1106 in 0e1e697

remote_name = output.strip()

evaluates to origin (as it must do so commonly). The subsequent line will attempt to transform the full remote branch name (remote name + branch name) into just the branch name. If you have a branch name which starts with any combination of the characters o,r,i,g,n, then lstrip() can potentially strip those characters away as well.

For example, given remote_name = origin, and rev_parse_output = origin/games, "origin/games".lstrip("origin/") will evaluate to "ames", causing the wrong branch to be pushed. This bug should be fairly easy to reproduce.

EDIT: Opened #849 for fix

[fcollonval]

Fixed by #849