get short sha of commit with gitpython

Question

The long SHA can be gotten like below:

repo = git.Repo(search_parent_directories=True)
sha = repo.head.object.hexsha

Or, in git 3.1.7:

sha = repo.head.commit.hexsha

How about short one? (short SHA is decided by the scale of the repo, so it should not be like sha[:7])

Answer 1

As far as I can tell, the gitpython Commit object does not support the short sha directly. However, you can use still gitpython's support for calling git directly to retrieve it (as of git 3.1.7):

repo = git.Repo(search_parent_directories=True)
sha = repo.head.commit.hexsha
short_sha = repo.git.rev_parse(sha, short=4)

This is the equivalent of running

git rev-parse --short=4 ...

on the command-line, which is the usual way of getting the short hash. This will return the shortest possible unambiguous hash of length >= 4 (You could pass in a smaller number, but since git's internal min is 4 it will have the same effect).

Answer 2

You will need to use the short argument of rev-parse here to generate the smallest SHA that can uniquely identify the commit. Basically, the short will call the internal git API and return the shortest possible length string for the SHA which can uniquely identify the commit, even if you've passed a very small value for short. So effectively, you can do something like below, which will give you the shortest SHA always (I use short=1 to emphasize that):

In [1]: import git
In [2]: repo = git.Repo(search_parent_directories=True)
In [3]: sha = repo.head.object.hexsha
In [4]: short_sha = repo.git.rev_parse(sha, short=1)
In [5]: short_sha
Out[5]: u'd5afd'

You can read more about this from the git side here. Also, as mentioned in the man-page for git-rev-parse, --short will by default take 7 as its value, and minimum 4.

--short=number

Instead of outputting the full SHA-1 values of object names try to abbreviate them to a shorter unique name. When no length is specified 7 is used. The minimum length is 4.