Add git merge-base command into GitPython

[jwir3]

It would be nice if there was a way in the GitPython API to do the following native git command:

git merge-base <commit 1> <commit 2>

For example, it would be nice to be able to perform the following:

from git import *

repo = Repo('/path/to/repo')
base = repo.find_last_common_ancestor('de1f33', '78dd34')
print(base)

The expected output, assuming the least common ancestor of 'de1f33' and '78dd34' was '6ff871', (obviously all of these commits have fictional SHAs) would be:

<git.Commit "6ff871652e0f3b9fa991bbd9b42e520f91723436e">

[ereOn]

Note that the merge-base command does not take only two commits but any number of commits so the implemented solution should offer that possibility as well.

[Byron]

Repo.merge_base() was implemented, including a rather straightforward test-case.
All the requested are supported, after all, I am just calling the cgit implementation and interpret its return values.

[Byron]

You can watch the development video on youtube

[sonicfly]

This implementation doesn't support "--is-ancestor" flag very well, it returns empty list for both 0 and 1 status code case.

[Byron]

Can you please open a new issue with some information about the version of GitPython and python you are using, along with how I can reproduce the issue ?
Thanks a lot !

[lahirug]

Does this support getting the common ancestor commit of two given branches ?
ex: git merge-base origin/release/1.30 origin/release/1.31
639ea92cd1c57f056e9e1a1a237fdef22533f53