I have a repository with branches master and A and lots of merge activity between the two. How can I find the commit in my repository when branch A was created based on master?
My repository basically looks like this:
-- X -- A -- B -- C -- D -- F (master)
\ / \ /
\ / \ /
G -- H -- I -- J (branch A)
I'm looking for revision A, which is not what git merge-base (--all) finds.
Surely I'm missing something, but, all the problems are caused because we are always trying to find the branch point going back in the history, and that causes all sort of problems because of the merging combinations available.
Instead, I've followed a different approach, based in the fact that both branches share a lot of history, exactly all the history before branching is 100% the same, so instead of going back, my proposal is about going forward (from 1st commit), looking for the 1st difference in both branches. The branch point will be, simply, the parent of the first difference found.
In practice:
#!/bin/bash
diff <( git rev-list "${1:-master}" --reverse --topo-order ) \
<( git rev-list "${2:-HEAD}" --reverse --topo-order) \
--unified=1 | sed -ne 's/^ //p' | head -1
I seem to be getting some joy with
git rev-list branch...master
The last line you get is the first commit on the branch, so then it's a matter of getting the parent of that. So
git rev-list -1 `git rev-list branch...master | tail -1`^
Seems to work for me and doesn't need diffs and so on (which is helpful as we don't have that version of diff)
Correction: This doesn't work if you are on the master branch, but I'm doing this in a script so that's less of an issue