Add --proceed flag to git-delete-squashed-branches

[nkiesel]

Fixes #1133

[hyperupcall]

The code change itself LGTM, but I'm wondering if this is the right approach

To me, it seems the behavior with --proceed is what is expected when running the command. If there is 10 branches that should be deleted, I do not think it should stop on the first one, if the first one fails to delete, by default. Maybe the best approach is to just add || true to the git branch -D "$branch" because it is more intuitive? It would also match the behavior in git-delete-branch.

@spacewander what do you think?

[hyperupcall]

Oops, I didn't realize there was disussion about this in #1133. I've added the reference to PR description

[nkiesel]

Yes, I would have preferred making this the default behavior. However, I was afraid that this breaks compatibility, so opted for a non-default option. Alternative could be to also support an env variable which changes the default behavior.

[hyperupcall]

@nkiesel I agree, backwards compatability is important. In my opinion, it is OK because the fix restores the command behavior to what is expected when this command runs, especially as these commands are typically run interactively and the behavior and flags remain the same as similar commands like git-delete-{branch,merged-branches}.

I'm not going to block on this issue, the final verdict is up to @spacewander. We can always make a change later that will change the default behavior, which will both be backwards-compatible to, and obsolete, the --proceed flag. Perhaps these can be aggregated into a single change for a major release.

[spacewander]

Let's merge this one first 😄