Allow passing a base branch that doesn't have version info

[Jackenmen]

Resolves #69

I could add enforcement of something here if this is too lax but I'm not sure what kind of check that could be. I suppose I could also add an option to .cherry_picker.toml that needs to be explicitly enabled to allow passing non-version branches if that makes it any better.

I'm aware this issue wasn't accepted but I kinda felt like doing it anyway, even if it doesn't end up merged :P

[Mariatta]

I think this change is reasonable.

[Jackenmen]

Tests are currently failing on main and so this PR is affected, I fixed them in #76.

[Mariatta]

I think allowing it to be configured via the toml file is a good idea as well. Would you be able to add that in a separate PR?

[Jackenmen]

I can do it here or in a separate PR, whatever you prefer. Can probably get to it tomorrow.

I assume you would want this to be a true/false setting determining whether branches without version info are allowed (defaulting to false to keep the current behavior intact)?

[Mariatta]

I think it should support the original behavior if not supplied.

[Jackenmen]

Alright, I added a require_version_in_branch_name option. Quite a mouthful but I couldn't really come up with anything else that was still clear about what the option is. At most I could maybe manage to make the name 4-5 characters shorter but the names I came up with were, in my opinion, a lot more vague than the current name.

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While looking into this, I also realized that I suggested adding such an option in the PR's description which I didn't really realize when you asked me to add it :smile:

[Jackenmen]

I created https://github.com/python/miss-islington/pull/639 to make miss-islington work with this PR since I realized that this is going to be necessary now that this also adds a new configuration option.