- Introduce `gitDiff` variable as a mockable wrapper for `git.Diff`.
- Update tests to use `withMockGitDiff` for injecting diff mocks.
- Minor flag description tweak for clarity.
- Introduce git.Diff function that uses CombinedOutput and treats exit code 1 as success (indicating changes exist).
- Update prdescribe command to use git.Diff and trim whitespace when checking for empty diffs.
- Enhance prdescribe output to include base branch in the status message.