There is GitPython. Haven’t heard of it before and internally, it relies on having the git executables somewhere; additionally, they might have plenty of bugs. But it could be worth a try.

How to clone:

import git  # pip install gitpython
git.Git("/your/directory/to/clone").clone("git://gitorious.org/git-python/mainline.git")

(It’s not nice and I don’t know if it is the supported way to do it, but it worked.)

GitPython uses a keyword args transformation under the hood:

# cmd.py
def transform_kwarg(self, name: str, value: Any, split_single_char_options: bool) -> List[str]:
    if len(name) == 1:
        if value is True:
            return ["-%s" % name]
        elif value not in (False, None):
            if split_single_char_options:
                return ["-%s" % name, "%s" % value]
            else:
                return ["-%s%s" % (name, value)]
    else:
        if value is True:
            return ["--%s" % dashify(name)]
        elif value is not False and value is not None:
            return ["--%s=%s" % (dashify(name), value)]
    return []

A resulting list of command parts is fed into subprocess.Popen, so you do not want to add --single-branch to the repo URL. If you do, a strange list will be passed to Popen. For example:

['-v', '--branch=my-branch', 'https://github.com/me/my-project.git --single-branch', '/tmp/clone/here']

However, armed with this new information, you can pass any git CLI flags you like just by using the kwargs. You may then ask yourself, "How do I pass in a dash to a keyword like single-branch?" That's a no-go in Python. You will see a dashify function in the above code which transforms any flag from, say, single_branch=True to single-branch, and then to --single-branch.

Full Example:

Here is a useful example for cloning a single, shallow branch using a personal access token from GitHub:

repo_url = "https://github.com/me/private-project.git"
branch = "wip-branch"
# Notice the trailing : below
credentials = base64.b64encode(f"{GHE_TOKEN}:".encode("latin-1")).decode("latin-1")
Repo.clone_from(
    url=repo_url,
    c=f"http.{repo_url}/.extraheader=AUTHORIZATION: basic {credentials}",
    single_branch=True,
    depth=1,
    to_path=f"/clone/to/here",
    branch=branch,
)

The command list sent to Popen then looks like this:

['git', 'clone', '-v', '-c', 'http.https://github.com/me/private-project.git/.extraheader=AUTHORIZATION: basic XTE...UwNTo=', '--single-branch', '--depth=1', '--bare', '--branch=wip-branch', 'https://github.com/me/private-project.git', '/clone/to/here']

(PSA: Please do not actually send your personal tokens as part of the URL before the @.)