From: Adr3nal D0S <adr3nald0s@gmail.com>
Date: Fri, 27 Jun 2008 14:55:51 GMT
Subject: Determining if two commits are on a separate branch
Message-ID: <308083c30806270755t4316be67u1f468b51bf475d28@mail.gmail.com>

We are making extensive use of submodules at work and we have created
a number of extra scripts to simplify our usage.  For example, there
is git-rstatus, which recursively reports status of all submodules.

I am working on another script to check whether or not a change to any
submodules jump branches.  If we have commits like this:

A--B--C
   \--D

I don't care if a submodule moves from A to C or B to C, but I do care
if a commit of the super-project would cause a jump from D to C or
revert from C to B, effectively dropping previously committed code on
the floor.

So, is there a "correct" or "best" way to determine if one commit's
SHA follows directly from another's SHA in the commit history?