git source: support fetching commit hash on a branch

docs/usage.rst

@@ -666,12 +666,18 @@ 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.
+This enables you to check tags or branch commits of an arbitrary git repository, also useful for scenarios like a github project having too many tags.
 
 git
   URL of the Git repository.
 
-This source returns tags and supports :ref:`list options`.
+use_commit
+  Return a commit hash instead of tags.
+
+branch
+  When ``use_commit`` is true, return the commit on the specified branch instead of the default one.
+
+When this source returns tags (``use_commit`` is not true) it supports :ref:`list options`.
 
 Check container registry
 ~~~~~~~~~~~~~~~~~~~~~~~~

nvchecker_source/git.py

@@ -7,7 +7,19 @@ async def get_version(
   name, conf, *, cache, keymanager=None
 ):
   git = conf['git']
-  cmd = f"git ls-remote -t --refs {git}"
+
+  use_commit = conf.get('use_commit', False)
+  if use_commit:
+    ref = conf.get('branch')
+    if ref is None:
+      ref = 'HEAD'
+    else:
+      ref = 'refs/heads/' + ref
+    cmd = f"git ls-remote {git} {ref}"
+    data = await cache.get(cmd, run_cmd)
+    return data.split(None, 1)[0]
+  else:
+    cmd = f"git ls-remote --tags --refs {git}"
     data = await cache.get(cmd, run_cmd)
     versions = [line.split("refs/tags/")[1] for line in data.splitlines()]
     return versions

tests/test_git.py

@@ -9,3 +9,18 @@ async def test_git(get_version):
         "source": "git",
         "git": "https://gitlab.com/gitlab-org/gitlab-test.git",
     }) == "v1.1.1"
+
+async def test_git_commit(get_version):
+    assert await get_version("example", {
+        "source": "git",
+        "git": "https://gitlab.com/gitlab-org/gitlab-test.git",
+        "use_commit": True,
+    }) == "ddd0f15ae83993f5cb66a927a28673882e99100b"
+
+async def test_git_commit_branch(get_version):
+    assert await get_version("example", {
+        "source": "git",
+        "git": "https://gitlab.com/gitlab-org/gitlab-test.git",
+        "use_commit": True,
+        "branch": "with-executables",
+    }) == "6b8dc4a827797aa025ff6b8f425e583858a10d4f"