Support Commit Amends

[sorascode]

This PR adds support for Commit Amends.

This is a draft until the Engine PR is merged.

Related Engine PR: godotengine/godot#117968
Related Git Plugin PR: godotengine/godot-git-plugin#323

[dsnopek]

Thanks!

However, we don't really do one-off changes to the extension_api.json like this. When a Godot version hits beta, then we start regularly synchronizing with the extension_api.json from beta and rc releases.

Otherwise, if folks want to use a custom extension_api.json, they should do it one of the usual ways, for example, via scons custom_api_file=path/to/my/extension_api.json

[sorascode]

Understood! Thanks for the info :)