Issue: ohmyzsh/ohmyzsh#12627
This commit refactors the prior implementation which used git aliases and modified .gitconfig. This implementation uses proper git-dash commands, which are all just symlinks to one handler - omz_git_commit.
BREAKING CHANGE: Prior to this commit, git aliases were not being
updated after every update of oh-my-zsh. In case you were using
git-commit plugin before this commit, please remove your git aliases to
proceed.