Look for all 3 git conflict markers in check_merge_conflict.

pre_commit_hooks/check_merge_conflict.py

@@ -9,11 +9,10 @@ from pre_commit_hooks.util import cmd_output
 
 CONFLICT_PATTERNS = [
     b'<<<<<<< ',
-    b'======= ',
-    b'=======\r\n',
-    b'=======\n',
+    b'=======',
     b'>>>>>>> ',
 ]
+N = len(CONFLICT_PATTERNS)
 
 
 def is_in_merge() -> bool:
@@ -40,15 +39,21 @@ def main(argv: Sequence[str] | None = None) -> int:
     retcode = 0
     for filename in args.filenames:
         with open(filename, 'rb') as inputfile:
+            expected_conflict_pattern_index = 0
             for i, line in enumerate(inputfile, start=1):
-                for pattern in CONFLICT_PATTERNS:
-                    if line.startswith(pattern):
+                # Look for conflict patterns in order
+                if line.startswith(
+                    CONFLICT_PATTERNS[expected_conflict_pattern_index]
+                ):
+                    expected_conflict_pattern_index += 1
+                    if expected_conflict_pattern_index == N:
                         print(
-                            f'{filename}:{i}: Merge conflict string '
-                            f'{pattern.strip().decode()!r} found',
+                            f"{filename}:{i}: Merge conflict string "
+                            f"{CONFLICT_PATTERNS[-1].strip().decode()!r} "
+                            f"found",
                         )
                         retcode = 1
-
+                        break
     return retcode
 
 

tests/check_merge_conflict_test.py

@@ -105,18 +105,29 @@ def test_merge_conflicts_git(capsys):
     assert main(['f1']) == 1
     out, _ = capsys.readouterr()
     assert out == (
-        "f1:1: Merge conflict string '<<<<<<<' found\n"
-        "f1:3: Merge conflict string '=======' found\n"
         "f1:5: Merge conflict string '>>>>>>>' found\n"
     )
 
 
 @pytest.mark.parametrize(
-    'contents', (b'<<<<<<< HEAD\n', b'=======\n', b'>>>>>>> main\n'),
+    # Individual markers are not actually merge conflicts, need 3 markers
+    # to mark a real conflict
+    'contents, expected_retcode',
+    ((b'<<<<<<< ', 0),
+     (b'=======', 0),
+     (b'>>>>>>> ',0),
+     # Real conflict marker
+     (b'<<<<<<< HEAD\n=======\n>>>>>>> branch\n', 1),
+     # Allow for the possibility of an .rst file with a =======
+     # inside a conflict marker
+     (b'<<<<<<< HEAD\n=======\n=======\n>>>>>>> branch\n', 1),
+    )
 )
-def test_merge_conflicts_failing(contents, repository_pending_merge):
-    repository_pending_merge.join('f2').write_binary(contents)
-    assert main(['f2']) == 1
+def test_merge_conflicts_with_rst(
+    contents, expected_retcode, repository_pending_merge
+):
+    repository_pending_merge.join('f2.rst').write_binary(contents)
+    assert main(['f2.rst']) == expected_retcode
 
 
 @pytest.mark.parametrize(
@@ -138,11 +149,19 @@ def test_does_not_care_when_not_in_a_merge(tmpdir):
     f.write_binary(b'problem\n=======\n')
     assert main([str(f.realpath())]) == 0
 
-
-def test_care_when_assumed_merge(tmpdir):
+@pytest.mark.parametrize(
+    'contents, expected_retcode',
+    (
+        # Not a complete conflict marker
+        (b'=======', 0),
+        # Complete conflict marker
+        (b'<<<<<<< HEAD\nproblem\n=======\n>>>>>>> branch\n', 1),
+    )
+)
+def test_care_when_assumed_merge(contents, expected_retcode, tmpdir):
     f = tmpdir.join('README.md')
-    f.write_binary(b'problem\n=======\n')
-    assert main([str(f.realpath()), '--assume-in-merge']) == 1
+    f.write_binary(contents)
+    assert main([str(f.realpath()), '--assume-in-merge']) == expected_retcode
 
 
 def test_worktree_merge_conflicts(f1_is_a_conflict_file, tmpdir, capsys):