A shortcut to create a GitHub PR to the parent branch

[radeusgd]

When using GitMachete with a deeper branch structure tree, I relatively often find myself wanting to create a PR from the current branch to its parent.

When launching GitHub after pushing the branch to the remote, I get a nice shortcut to create a PR from the recently pushed branch. But that shortcut defaults the base branch to be the default branch of the repo (develop / master / main / whatever it is). However, with the Machete workflow it usually makes sense to create the PR not to the default main branch but instead to the parent (as in the machete file structure).

I often use the GH shortcut and forget to change the PR base to the proper branch. It's also not that easy to find the parent branch in our repo when there are a lot of branches.

It would be a super cool addition to the Machete IntelliJ plugin if we had a button that allowed us to create a GH PR of the current branch to its parent, essentially opening the page https://github.com/<my org>/<my repo>/compare/<parent branch from Machete file>...<my current branch>.

[PawelLipski]

GitHub support is long pending, #56 😅 but indeed we can implement just this functionality as the first step.

Problems to consider:

• whether to rely on IntelliJ GitHub plugin (with its unstable APIs... rel Github PR integration #1293) or to use some Java client independent of GitHub
• whether to display the Open GitHub PR button for the branches that already have a PR opened (how to detect whether it exists?)
• (minor) detect whether the remote for the given repo corresponds to GitHub (easy for github.com, more problematic for GitHub Enterprise instances)