feat(git_patch_parser): add Git patch parsing functionality

- Introduce a data model for structured representation of Git patches
- Implement a parser to extract key fields from patch text
- Add unit tests to ensure robustness and validate edge cases

tests/test_parser.py

@@ -0,0 +1,78 @@
+import unittest
+from patchman.utils.git_patch_parser.parser import parse_git_patch
+from patchman.utils.git_patch_parser.models import GitPatch
+
+class TestGitPatchParser(unittest.TestCase):
+    def test_parse_valid_patch(self):
+        patch_text = """From 0123456789abcdef1234567890abcdef12345678 Mon Sep 17 00:00:00 2001
+From: Max Mustermann <max@example.com>
+Date: Wed, 23 Jul 2025 12:34:56 +0200
+Subject: [PATCH] Dein Patch-Titel
+
+Dies ist eine Beschreibung des Patches.
+
+diff --git a/file.txt b/file.txt
+index 83db48f..f735c3b 100644
+--- a/file.txt
++++ b/file.txt
+@@ -1 +1 @@
+-Hello World
++Hello Patchman
+"""
+        expected_patch = GitPatch(
+            commit_hash="0123456789abcdef1234567890abcdef12345678",
+            author="Max Mustermann <max@example.com>",
+            date="Wed, 23 Jul 2025 12:34:56 +0200",
+            subject="[PATCH] Dein Patch-Titel",
+            description="Dies ist eine Beschreibung des Patches.",
+            diff="diff --git a/file.txt b/file.txt\nindex 83db48f..f735c3b 100644\n--- a/file.txt\n+++ b/file.txt\n@@ -1 +1 @@\n-Hello World\n+Hello Patchman\n"
+        )
+        parsed_patch = parse_git_patch(patch_text)
+        self.assertEqual(parsed_patch, expected_patch)
+
+    def test_parse_invalid_patch(self):
+        patch_text = "Invalid patch content"
+        with self.assertRaises(ValueError) as context:
+            parse_git_patch(patch_text)
+        self.assertIn("Commit hash not found", str(context.exception))
+
+    def test_parse_patch_missing_author(self):
+        patch_text = """From 0123456789abcdef1234567890abcdef12345678 Mon Sep 17 00:00:00 2001
+Date: Wed, 23 Jul 2025 12:34:56 +0200
+Subject: [PATCH] Test"""
+        with self.assertRaises(ValueError) as context:
+            parse_git_patch(patch_text)
+        self.assertIn("Author not found", str(context.exception))
+
+    def test_parse_patch_missing_date(self):
+        patch_text = """From 0123456789abcdef1234567890abcdef12345678 Mon Sep 17 00:00:00 2001
+From: Test Author <test@example.com>
+Subject: [PATCH] Test"""
+        with self.assertRaises(ValueError) as context:
+            parse_git_patch(patch_text)
+        self.assertIn("Date not found", str(context.exception))
+
+    def test_parse_patch_missing_subject(self):
+        patch_text = """From 0123456789abcdef1234567890abcdef12345678 Mon Sep 17 00:00:00 2001
+From: Test Author <test@example.com>
+Date: Wed, 23 Jul 2025 12:34:56 +0200"""
+        with self.assertRaises(ValueError) as context:
+            parse_git_patch(patch_text)
+        self.assertIn("Subject not found", str(context.exception))
+
+    def test_parse_patch_without_description_and_diff(self):
+        patch_text = """From 0123456789abcdef1234567890abcdef12345678 Mon Sep 17 00:00:00 2001
+From: Test Author <test@example.com>
+Date: Wed, 23 Jul 2025 12:34:56 +0200
+Subject: [PATCH] Minimal patch"""
+        
+        parsed_patch = parse_git_patch(patch_text)
+        self.assertEqual(parsed_patch.commit_hash, "0123456789abcdef1234567890abcdef12345678")
+        self.assertEqual(parsed_patch.author, "Test Author <test@example.com>")
+        self.assertEqual(parsed_patch.date, "Wed, 23 Jul 2025 12:34:56 +0200")
+        self.assertEqual(parsed_patch.subject, "[PATCH] Minimal patch")
+        self.assertEqual(parsed_patch.description, "")
+        self.assertEqual(parsed_patch.diff, "")
+
+if __name__ == '__main__':
+    unittest.main()