fix: changelog ignored branch's commits before merge

[iberflow]

If you ran care changelog on a feature branch before merging, it only listed the commits that were already on main. A branch with 15 commits past the last tag would show the 1 that had landed.

The reason is that care asked the git host for the commit list instead of reading your local checkout. The host can't see an unmerged branch, and when you pass HEAD it assumes you mean its default branch, so you got main's history back no matter where you were standing. That same mistake stripped author handles and pointed the compare link and contributor list at main.

Now care gets the commit list from local git and only asks the host to fill in author handles. When it does talk to the host, it sends the real branch name instead of HEAD.

Nothing changes about how you call it. One thing to know: on a branch you haven't pushed, the compare link will 404 instead of quietly pointing at main.