Add a git source

It's a thin wrapper around the cmd source, and reuses its get_cmd
function.

docs/usage.rst

@@ -641,6 +641,19 @@ strip_release
 
 Note that either pkg or srcpkg needs to be specified (but not both) or the item name will be used as pkg.
 
+Check Git repository
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+::
+
+  source = "git"
+
+This enables you to check tags of an arbitrary git repository, also useful for scenarios like a github project having too many tags.
+
+url
+  URL of the Git repository.
+
+This source returns tags and supports :ref:`list options`.
+
 Manually updating
 ~~~~~~~~~~~~~~~~~
 ::

nvchecker_source/git.py

@@ -0,0 +1,15 @@
+# MIT licensed
+# Copyright (c) 2020 Felix Yan <felixonmars@archlinux.org>, et al.
+
+import re
+from nvchecker_source.cmd import run_cmd
+
+async def get_version(
+  name, conf, *, cache, keymanager=None
+):
+  git = conf['git']
+  cmd = f"git ls-remote -t --refs {git}"
+  data = await cache.get(cmd, run_cmd)
+  regex = "(?<=refs/tags/).*$"
+
+  return re.findall(regex, data)

tests/test_git.py

@@ -0,0 +1,11 @@
+# MIT licensed
+# Copyright (c) 2020 Felix Yan <felixonmars@archlinux.org>, et al.
+
+import pytest
+pytestmark = [pytest.mark.asyncio, pytest.mark.needs_net]
+
+async def test_git(get_version):
+    assert await get_version("example", {
+        "source": "git",
+        "git": "https://gitlab.com/gitlab-org/gitlab-test.git",
+    }) == "v1.1.1"