Finding a branch point with Git

For complicated branches, there might be more than one boundary. It's suggested to add a "tail -n 1" to get the last boundary.

git rev-list --boundary HEAD...master | grep ^- | cut -c2- | tail -n 1

(This command was found incorrect in some case, multiple boundary found, but the last boundary wasn't the desired one, but the second last.)

Determining if a Git repository contains a particular commit - Stack Overflow
http://stackoverflow.com/questions/3506082/determining-if-a-git-repository-contains-a-particular-commit

if [ "$(git rev-parse $commitA)" == "$(git merge-base $commitA $commitB)" ]; then ...; else ...; fi

"git merge-base" will also get the result of finding the branch point, for merge-base is the branch point of the two branches.

git merge-base $commitA $commitB

http://stackoverflow.com/questions/1527234/finding-a-branch-point-with-git

git rev-list --boundary branch-a...master | grep ^- | cut -c2-

or add it to aliases in ~/.gitconfig :

[alias]
diverges = !sh -c 'git rev-list --boundary $1...$2 | grep ^- | cut -c2-'

so I can call it as:

git diverges branch-a master