Reference Git branch start commit

Question

I am trying to find how to reference branch start commit from script. I mean the commit sha at which branch was forked.

Moreover I expect it work for history made fr

Answer 1

What you're looking for is the command merge-base:

git merge-base master feature-branch

will print the best common ancestor of those two branches, i.e. where they forked apart. (The documentation has pretty pretty pictures to clarify some of the interesting cases)