Remove support of Git 2.18 and earlier versions

We maintained non-obvious code to support versions of Git that did not
have the `--only-matching` option, which appeared in Git 2.19. This
version was released in September 2018, it's time to move on.

CHANGES.rst

@@ -3,6 +3,9 @@
 
 - Add support of Python 3.12.
 
+- |backward-incompatible| Remove support of Git 2.18 and earlier
+  version. You must now have Git 2.19 (or a more recent version).
+
 - |backward-incompatible| Remove support of Python 3.7.
 
 - |backward-incompatible| Remove ``--xunit-file`` argument from all

docs/installation.rst

@@ -1,9 +1,7 @@
 Installation
 ============
 
-You must have Python 3.8 or later, and a relatively recent version of
-Git. Git 2.1.4 (shipped with Debian Jessie) is known to work. More
-recent versions should work and are supported.
+You must have Python 3.8 or later, and Git 2.19.0 or later.
 
 Install with ``pip``, preferably in a `virtual environment`_:
 

src/check_oldies/annotations.py

@@ -2,11 +2,8 @@
 import dataclasses
 import datetime
 import re
-import subprocess
 import typing
 
-import pkg_resources
-
 from . import commands
 from . import output
 
@@ -230,66 +227,28 @@ def get_known_future_tags(directory, annotation_regex, future_tag_regex, whiteli
     return set(lines)
 
 
-def git_supports_only_matching():
-    out = subprocess.check_output(["git", "--version"]).decode("utf-8")
-    # output looks like "git version 2.26.0"
-    git_version = pkg_resources.parse_version(out.split()[2])
-    # `git grep --only-matching` appeared in Git 2.19.0
-    # https://github.com/git/git/blob/v2.19.0/Documentation/RelNotes/2.19.0.txt#L41
-    minimal_version = pkg_resources.parse_version("2.19.0")
-    return git_version >= minimal_version
-
-
 def get_all_futures(directory, future_tag_regex, whitelist):
     """Get all occurrences of FUTURE tags."""
-    # Old versions of Git (such as Git 2.1.4 that is shipped by Debian
-    # Jessie) do not support the `--only-matching` option. Pipe to
-    # `sed` instead.
-    if git_supports_only_matching():
-        grep = [
-            "git",
-            "grep",
-            "-I",  # ignore binary files
-            "--line-number",
-            "--extended-regexp",
-            "--only-matching",
-            "-e",
-            future_tag_regex,
-            "--and",
-            "--not",
-            "-e",
-            IGNORE_PRAGMA,
-        ]
-        grep.extend([f":(exclude){glob}" for glob in whitelist])
-        lines = commands.get_output(
-            grep,
-            cwd=directory,
-            valid_return_codes=(0, 1),  # 0 if there are matches, 1 otherwise
-        )
-    else:
-        grep = [
-            "git",
-            "grep",
-            "-I",  # ignore binary files
-            "--line-number",
-            "--extended-regexp",
-            "-e",
-            future_tag_regex,
-            "--and",
-            "--not",
-            "-e",
-            IGNORE_PRAGMA,
-            "--",  # needed on old versions...
-            ".",  # ... of git
-        ]
-        grep.extend([f":(exclude){glob}" for glob in whitelist])
-        sed = f'sed --regexp-extended "s/(.*?):.*?({future_tag_regex}).*?/\\1:\\2/g"'
-        lines = commands.get_pipe_command_output(
-            grep,
-            piped_to=sed,
-            cwd=directory,
-            valid_return_codes=(0, 1),  # 0 if there are matches, 1 otherwise
-        )
+    grep = [
+        "git",
+        "grep",
+        "-I",  # ignore binary files
+        "--line-number",
+        "--extended-regexp",
+        "--only-matching",
+        "-e",
+        future_tag_regex,
+        "--and",
+        "--not",
+        "-e",
+        IGNORE_PRAGMA,
+    ]
+    grep.extend([f":(exclude){glob}" for glob in whitelist])
+    lines = commands.get_output(
+        grep,
+        cwd=directory,
+        valid_return_codes=(0, 1),  # 0 if there are matches, 1 otherwise
+    )
 
     occurrences = collections.defaultdict(list)
     for line in lines:

tests/test_annotations.py

@@ -67,15 +67,3 @@ def test_get_login_from_committer_email():
     assert login == "<@example.com>"  # should not be the empty string
     login = annotations.get_login_from_committer_email("John Smith")
     assert login == "John Smith"
-
-
-def test_git_supports_only_matching():
-    # We expect tests to run on a system that has a recent version of Git.
-    assert annotations.git_supports_only_matching()
-
-
-@mock.patch("check_oldies.annotations.git_supports_only_matching", lambda: False)
-def test_old_git_without_only_matching():
-    path = base.TEST_DIR_PATH / "data/project4"
-    futures = annotations.get_all_futures(path, base.TESTING_FUTURE_TAG, whitelist=[])
-    assert set(futures.keys()) == {"FEWTURE-BOOM", "FEWTURE-I-AM-AN-ORPHAN"}