feat(changelog): support excluding pathspecs

[vjymisal0]

Summary

Add -e/--exclude <pathspec> to git changelog so vendored subtrees and other files/directories can be omitted from generated changelogs. The option may be supplied multiple times and uses Git pathspec exclude syntax. Existing invocations remain unchanged.

Verification

• bash -n bin/git-changelog
• ./check_integrity.sh changelog
• Manual regression: --exclude vendor omits vendor-only commits, while the default invocation still includes them.
• git diff --check
• make test could not run because bats is not installed in the environment.

Commit includes DCO signoff.

Fixes #1199

[spacewander]

LGTM. Please update tests and https://github.com/tj/git-extras/blob/main/etc/git-extras-completion.zsh

[vjymisal0]

Thanks @spacewander! I added Bats coverage for excluding commits by pathspec and updated the zsh completion for -e/--exclude. The change is pushed in 7ac4233 with DCO sign-off. I also verified the changelog script with bash syntax checking and a manual exclusion case; the full Bats suite could not run here because bats is not installed.

[vjymisal0]

Thanks @spacewander — added tests and updated shell completion/documentation for changelog pathspec exclusions. The branch is clean and pushed.