Find first common child of two commits

Question

           :
           A
T         / \\
i        B   C
m        :   :
e        D   E
          \\ /
|          F
V          :

git merge-base

Answer 1

Oops. Didn't read that carefully enough.

The only information in a commit is the id of its parent (or parents). You cannot get to a child from a parent commit (this is the directed part of the repository being a DAG).

Looking at this more - it looks like the --ancestry-path option for git log can do this. For instance given:

* 85d26ab When compiling vim, also compile & install gvim
*   3146e5d Merge remote-tracking branch 'origin/devel' into deve
|\
| * 28d08e5 rebasing-merge: specify all commits explicitly
* | 006d11d Help 'file' find its magic file
|/
* e68531d (tag: Git-1.7.6-preview20110720) Update submodules

we can get the all children of these two commits using

git log --oneline --ancestry-path B..E

if you then reverse this and pick off the first one -- that is F.

git rev-list --reverse --ancestry-path 28d08e5..006d11d | head -1

in my case that returns 3146e5d.