Improve asserting if branches are synced by checking `git log X..Y` both ways.

[levibostian]

Today, when the script runs git rebase and then runs git log X..Y to check if the branches are identical, the script should also check git log Y..X. Because there is a chance that branch X is behind and ahead in commits compared to branch Y.

[levibostian]

I implemented this but then realized that we don't want this change to happen.

The use case of this tool is to make sure that the ahead branch commits are put into the behind branch. There are use cases where the ahead branch being behind the behind branch is OK.

Let's say that you use the beta branch for the latest beta deployment while the default branch is develop.

Let's say that the latest beta deployment was 3 weeks ago and you have been developing features in develop ever since the latest beta which means that develop is ahead of beta (and that's OK!). You then find a bug in beta so you add a bug fix commit into the beta branch. beta is now ahead of develop and you want to put that 1 commit into develop. So, you use this tool to do that. You set beta as the ahead branch and develop as the behind branch. This tool copies over that 1 commit and the job is done. It's OK for beta to remain behind from develop! If you want them to be truly identical, you would run this tool twice:

name: Sync release branches with develop

on: [push]

jobs:
  sync-branches:
    name: Sync branches 
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - uses: levibostian/action-sync-branches@v1
        with:
          behind: develop
          ahead: beta 
          githubToken: ${{ secrets.BOT_PUSH_TOKEN }}
      - uses: levibostian/action-sync-branches@v1
        with:
          behind: beta
          ahead: develop 
          githubToken: ${{ secrets.BOT_PUSH_TOKEN }}