git_ui: When no changes, disable stage/unstage toolbar buttons

[Simek]

Why

While working on recent PR I have spotted that "Stage" and "Unstage" buttons in "Uncommited Changes" toolbar are always active, even when there is no changes made locally.

How

Re-use already existing button states for managing the disabled state of "Uncommited Changes" toolbar buttons when changeset is empty.

Release Notes:

• Added disabled state for "Uncommited Changes" toolbar buttons when there are no changes present

Preview

[cole-miller]

Thanks for opening a PR!

However, note that it's intentional that we don't disable those buttons, see #26936 and the issue that's responding to. The thought is that when you're going through the hunks, you should be able to StageAndNext with the mouse even if a hunk is already staged. Otherwise, you'd have to move your mouse repeatedly back and forth between Stage and the down arrow button in the case where there are lots of hunks in a row that you want to keep, some of them already staged.

[Simek]

Hey @cole-miller, thanks for the explanation and more context on that code! 🙏

I have change the code to achieve the initial part mentioned in "Why" section, so buttons being enabled with no local changes. I have used the combination of nav button and stage/unstage all, which should only disable them when both of those button are disabled, and retain the previous bechaviour when there are changes present.

Let me know what do you think about this approach, I'm also fine with closing this PR. 🙂

[cole-miller]

Thanks!