Refactor determination of the oldest commit to operate on.
Refactor determination of the oldest commit to operate on.

Instead of some git-log(1) magic, just use a straight loop and examine the commits
one-by-one ourselves.

Fixes a bug: if HEAD was a commit of mine and there was another local commit of
mine on top of that, the script wouldn't correctly determine the last commit to
operate on.

danielshahaf/zsh-dev