Merge all branches into the base branch of a chain

[pcarranzav]

Sometimes we work on large chains of PRs that all get reviewed and approved in parallel.
At the end of the process, we merge all of them into the base branch and then push that, which effectively merges all of the chain PRs - we do this in order so that all of the merges are fast-forwards.
For this it would be useful to have a git chain merge-all (or maybe git chain collapse?).
Would others find this useful?

(Note this is different to #11 as that one is about merging the latest dependency branch into each chain branch, whereas here it's about merging all branches in the chain into the base branch)

[pcarranzav]

Thinking about it more, just merging isn't sufficient... for each branch that is merged, you need to push it and then delete the branch on GitHub for GitHub to change the target in the subsequent PRs 🤔

(Update: if the repo on GitHub is configured to auto-delete branches, merging and pushing one branch at a time starting from the one closest to the base would do the trick)