Add github commands that would trigger specific actions

[ksolana]

See how swift does it: https://github.com/apple/llvm-project does it. We could have commands to run lint, premerge checks etc.

• @check-lint: run the linter (clippy + fmt).
• @check-pre-merge: run all the pre-merge checks. Essentially run all the checks we run already. This is useful if we want to rerun all the checks without updating the patch.
• @help
• @format-code (formats the code and commits to the PR). We don't have to do this one. As long as we are failing the pre-merge check (which we are already) in case of formatting errors.
• @rebase: Rebase the patch on top of main. This would also trigger all the tests upon successful rebase. I think github already has this feature but i'm not sure why it doesn't show up already. see: https://github.blog/changelog/2022-02-03-more-ways-to-keep-your-pull-request-branch-up-to-date/

[yihau]

Just created a POC here: yihau#1. Does this do what we expect? (I use ! instead of @ to avoid at some wrong people accidentally. also only implement help and check-lint there)

btw, what's check-pre-merge for?

[yihau]

let me create these issues separately so that we can focus on single topic in each individual issue.

[yihau]

opened some issues and have some comments there. we can discuss there and close them as completed when we have PRs or other alternative methods to solve them

• [PR commands] check-lint #357
• [PR commands] check-pre-merge #358
• [PR commands] help #359
• [PR commands] format-code #360
• [PR commands] rebase #361