From aba94fe0a1245232fa4a67a0a6ae93c2576871c6 Mon Sep 17 00:00:00 2001
From: HausCloud <hauscloud.me@gmail.com>
Date: Tue, 7 Sep 2021 03:01:33 +0000
Subject: [PATCH] Add warning for git version parse failures

---
 news/10361.enhancement.rst   |  1 +
 src/pip/_internal/vcs/git.py |  1 +
 tests/unit/test_vcs.py       | 19 +++++++++++++++++++
 3 files changed, 21 insertions(+)
 create mode 100644 news/10361.enhancement.rst

diff --git a/news/10361.enhancement.rst b/news/10361.enhancement.rst
new file mode 100644
index 00000000000..4104b072f5f
--- /dev/null
+++ b/news/10361.enhancement.rst
@@ -0,0 +1 @@
+Add a warning upon failing to match (via regex) the current system's git version.
\ No newline at end of file
diff --git a/src/pip/_internal/vcs/git.py b/src/pip/_internal/vcs/git.py
index 3186553e705..2ca4e91f6f5 100644
--- a/src/pip/_internal/vcs/git.py
+++ b/src/pip/_internal/vcs/git.py
@@ -94,6 +94,7 @@ def get_git_version(self) -> Tuple[int, ...]:
         version = self.run_command(["version"], show_stdout=False, stdout_only=True)
         match = GIT_VERSION_REGEX.match(version)
         if not match:
+            logger.warning("Unable to parse '%s'.", version)
             return ()
         return tuple(int(c) for c in match.groups())
 
diff --git a/tests/unit/test_vcs.py b/tests/unit/test_vcs.py
index 0f41ba1d7c1..069ebd89ec6 100644
--- a/tests/unit/test_vcs.py
+++ b/tests/unit/test_vcs.py
@@ -299,6 +299,25 @@ def test_git_is_commit_id_equal(mock_get_revision, rev_name, result):
     assert Git.is_commit_id_equal("/path", rev_name) is result
 
 
+@pytest.mark.parametrize(
+    "version_out,result",
+    (
+        ("git version -2.25.1", ()),
+        ("git version 2.a.1", ()),
+        ("git ver. 2.25.1", ()),
+    ),
+)
+@patch("pip._internal.vcs.versioncontrol.VersionControl.run_command")
+def test_git_parse_fail_warning(mock_run_command, caplog, version_out, result):
+    """
+    Test Git.get_git_version().
+    """
+    mock_run_command.return_value = version_out
+    git_tuple = Git().get_git_version()
+    assert git_tuple == result
+    assert caplog.messages == ["Unable to parse '%s'." % version_out]
+
+
 # The non-SVN backends all use the same get_netloc_and_auth(), so only test
 # Git as a representative.
 @pytest.mark.parametrize(