Allow commit & push

[ktaletsk]

Implements #837

So, here's my take on enabling 'Commit and push' in place of 'Commit' button. I pass branch information along with boolean flag to GitCommitBox so that it can render 'Commit and Push' or display the error hint when applicable. Push action is added on the back of GitPanel.commitStagedFiles. There is also a new flag in extension settings to enable/disable this behavior.

Please, check the code and if it doesn't make sense, I am open to rewriting it.

[github-actions]

👈 Launch a binder notebook on branch ktaletsk/jupyterlab-git/commit-and-push

[fcollonval]

Thanks @ktaletsk

I added some suggestion to have a better API.

[fcollonval]

@meeseeksdev backport to jlab-2

[lumberbot-app]

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

$ git checkout jlab-2
$ git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

$ git cherry-pick -m1 6b95bc9dfd31e9a5e829100a411e563176624e56

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

$ git commit -am 'Backport PR #887: Allow `commit & push`'

4. Push to a named branch :

git push YOURFORK jlab-2:auto-backport-of-pr-887-on-jlab-2

5. Create a PR against branch jlab-2, I would have named this PR:

"Backport PR #887 on branch jlab-2"

And apply the correct labels and milestones.

Congratulation you did some good work ! Hopefully your backport PR will be tested by the continuous integration and merged soon!

If these instruction are inaccurate, feel free to suggest an improvement.