[Feature Request] Add change detection to qmk cformat

[skullydazed]

Currently qmk cformat without any additional arguments runs clang-format against everything. To make it easier and faster to use we should support detecting changes and run only against those files which have been edited.

Feature Request Type

• Core functionality
• Alteration (enhancement/optimization) of existing feature(s)

Description

When the user supplies a list of filenames (by running qmk cformat <file1> <file2> <...> <fileN>) the behavior should be unchanged.

When the user runs qmk cformat -a the command should behave exactly as running qmk cformat does today, by running clang-format against all core files.

When the user runs qmk cformat without any arguments we should use the output of git diff --name-only origin/master <core directories> to find the files to format. We should provide a new optional option --base-branch (-b) to specify a branch other than origin/master.

[skullydazed]

The behavior is still a WIP. I've written these down as a starting point but if there's an argument for doing it differently please suggest changes. For example, I'm not entirely fond of the name --master-branch but I'm wary of the implications of having user.branch overriding behavior here.

[noroadsleft]

I'd suggest --base-branch instead of --master-branch, because base branch is GitHub's term for the target of a pull request. The default branch of a repo isn't always going to be named master. -b alias still works IMO though.

[skullydazed]

I like that name a lot better.