feat: allow enforce minimum description length

README.md

@@ -89,6 +89,13 @@ The default maximum subject line length is 72 characters. Override with
 commit-guard --max-subject-length 100
 ```
 
+By default there is no minimum description length. Enforce one with
+`--min-description-length`:
+
+```bash
+commit-guard --min-description-length 10
+```
+
 ### Type validation
 
 By default the standard conventional commit types are accepted. Use `--types`
@@ -122,9 +129,9 @@ commit-guard --scopes auth,api --require-scope
 ### Configuration file
 
 Place `.commit-guard.toml` in your project root (or any parent directory) to
-set defaults for `enable`, `disable`, `scopes`, `require-scope`, `types`, and
-`max-subject-length`. commit-guard searches upward from the working directory
-and uses the first file found.
+set defaults for `enable`, `disable`, `scopes`, `require-scope`, `types`,
+`max-subject-length`, and `min-description-length`. commit-guard searches
+upward from the working directory and uses the first file found.
 
 ```toml
 # .commit-guard.toml
@@ -133,6 +140,7 @@ scopes = ["auth", "api", "db"]
 require-scope = true
 types = ["feat", "fix", "chore", "wip"]
 max-subject-length = 100
+min-description-length = 10
 ```
 
 ```toml
@@ -141,8 +149,8 @@ enable = ["subject", "imperative"]
 ```
 
 CLI flags (`--enable`, `--disable`, `--scopes`, `--require-scope`, `--types`,
-`--max-subject-length`) take full precedence and ignore config file values when
-provided.
+`--max-subject-length`, `--min-description-length`) take full precedence and
+ignore config file values when provided.
 
 ### Checking a range of commits
 

src/git_commit_guard/__init__.py

@@ -120,12 +120,13 @@ def _strip_comments(message):
     )
 
 
-def check_subject(  # noqa: PLR0913 Too many arguments in function definition (6 > 5)
+def check_subject(  # noqa: PLR0913 Too many arguments in function definition (7 > 5)
     line,
     result,
     allowed_scopes=frozenset(),
     allowed_types=TYPES,
     max_subject_length=MAX_SUBJECT_LEN,
+    min_description_length=0,
     *,
     require_scope=False,
 ):
@@ -150,6 +151,8 @@ def check_subject(  # noqa: PLR0913 Too many arguments in function definition (6
         result.error("description must not end with period")
     if len(line) > max_subject_length:
         result.error(f"subject too long: {len(line)} > {max_subject_length}")
+    if min_description_length > 0 and len(desc) < min_description_length:
+        result.error(f"description too short: {len(desc)} < {min_description_length}")
     return desc
 
 
@@ -250,6 +253,7 @@ class Args:
     require_scope: bool
     allowed_types: frozenset
     max_subject_length: int
+    min_description_length: int
     rev_range: str | None
     allow_empty: bool
     include_merges: bool
@@ -279,6 +283,14 @@ def _resolve_max_subject_length(args, config):
     return MAX_SUBJECT_LEN
 
 
+def _resolve_min_description_length(args, config):
+    if args.min_description_length is not None:
+        return args.min_description_length
+    if "min-description-length" in config:
+        return config["min-description-length"]
+    return 0
+
+
 def _resolve_types(args, config):
     if args.types:
         return frozenset(t.strip() for t in args.types.split(","))
@@ -350,6 +362,13 @@ def _parse_args():
         metavar="N",
         help=f"maximum subject line length (default: {MAX_SUBJECT_LEN})",
     )
+    parser.add_argument(
+        "--min-description-length",
+        type=int,
+        default=None,
+        metavar="N",
+        help="minimum description length in characters (default: 0, off)",
+    )
     parser.add_argument(
         "--range",
         dest="rev_range",
@@ -374,6 +393,7 @@ def _parse_args():
     allowed_scopes, require_scope = _resolve_scopes(args, config)
     allowed_types = _resolve_types(args, config)
     max_subject_length = _resolve_max_subject_length(args, config)
+    min_description_length = _resolve_min_description_length(args, config)
 
     if args.allow_empty and not args.rev_range:
         parser.error("--allow-empty requires --range")
@@ -406,6 +426,7 @@ def _parse_args():
         require_scope=require_scope,
         allowed_types=allowed_types,
         max_subject_length=max_subject_length,
+        min_description_length=min_description_length,
         rev_range=args.rev_range,
         allow_empty=args.allow_empty,
         include_merges=args.include_merges,
@@ -432,6 +453,7 @@ def _run_checks(args, rev, message, result):
             args.allowed_scopes,
             args.allowed_types,
             args.max_subject_length,
+            args.min_description_length,
             require_scope=args.require_scope,
         )
     if Check.IMPERATIVE in args.enabled:

tests/test_git_commit_guard.py

@@ -17,6 +17,7 @@
     _parse_config_checks,
     _report,
     _resolve_max_subject_length,
+    _resolve_min_description_length,
     _resolve_types,
     _strip_comments,
     check_body,
@@ -161,6 +162,22 @@ def test_custom_max_length_passes(self):
         check_subject("fix: ok", r, max_subject_length=10)
         assert r.ok
 
+    def test_min_description_length_zero_disables_check(self):
+        r = Result()
+        check_subject("fix: add x", r, min_description_length=0)
+        assert r.ok
+
+    def test_min_description_length_enforced(self):
+        r = Result()
+        check_subject("fix: add x", r, min_description_length=6)
+        assert not r.ok
+        assert any("description too short" in m for _, m in r.errors)
+
+    def test_min_description_length_exact_passes(self):
+        r = Result()
+        check_subject("fix: hello", r, min_description_length=5)
+        assert r.ok
+
     def test_custom_type_passes(self):
         r = Result()
         check_subject("wip: add thing", r, allowed_types=frozenset(["wip"]))
@@ -455,6 +472,32 @@ def test_cli_overrides_config(self):
         assert result == 50  # noqa: PLR2004 Magic value used in comparison, consider replacing 50 with a constant variable
 
 
+class TestResolveMinDescriptionLength:
+    def test_defaults_to_zero(self):
+        result = _resolve_min_description_length(
+            Namespace(min_description_length=None), {}
+        )
+        assert result == 0
+
+    def test_cli_flag_overrides_default(self):
+        result = _resolve_min_description_length(
+            Namespace(min_description_length=10), {}
+        )
+        assert result == 10  # noqa: PLR2004 Magic value used in comparison, consider replacing 10 with a constant variable
+
+    def test_config_overrides_default(self):
+        result = _resolve_min_description_length(
+            Namespace(min_description_length=None), {"min-description-length": 8}
+        )
+        assert result == 8  # noqa: PLR2004 Magic value used in comparison, consider replacing 8 with a constant variable
+
+    def test_cli_overrides_config(self):
+        result = _resolve_min_description_length(
+            Namespace(min_description_length=10), {"min-description-length": 8}
+        )
+        assert result == 10  # noqa: PLR2004 Magic value used in comparison, consider replacing 10 with a constant variable
+
+
 class TestResolveTypes:
     def test_defaults_when_no_config_or_flag(self):
         assert _resolve_types(Namespace(types=None), {}) == TYPES
@@ -812,6 +855,70 @@ def test_max_subject_length_cli_overrides_config(self, tmp_path):
         ):
             assert main() == 0
 
+    def test_min_description_length_flag_passes(self, tmp_path):
+        f = tmp_path / "msg"
+        f.write_text("fix: add thing\n\nbody\n\nSigned-off-by: A User <a@b.com>")
+        argv = [
+            "cg",
+            "--message-file",
+            str(f),
+            "--disable",
+            "signature",
+            "--min-description-length",
+            "5",
+        ]
+        with patch("sys.argv", argv):
+            assert main() == 0
+
+    def test_min_description_length_flag_fails(self, tmp_path):
+        f = tmp_path / "msg"
+        f.write_text("fix: add x\n\nbody\n\nSigned-off-by: A User <a@b.com>")
+        argv = [
+            "cg",
+            "--message-file",
+            str(f),
+            "--disable",
+            "signature,imperative",
+            "--min-description-length",
+            "6",
+        ]
+        with patch("sys.argv", argv):
+            assert main() == 1
+
+    def test_min_description_length_from_config(self, tmp_path):
+        f = tmp_path / "msg"
+        f.write_text("fix: add x\n\nbody\n\nSigned-off-by: A User <a@b.com>")
+        argv = ["cg", "--message-file", str(f), "--disable", "signature,imperative"]
+        with (
+            patch("sys.argv", argv),
+            patch(
+                "git_commit_guard._load_config",
+                return_value={"min-description-length": 6},
+            ),
+        ):
+            assert main() == 1
+
+    def test_min_description_length_cli_overrides_config(self, tmp_path):
+        f = tmp_path / "msg"
+        f.write_text("fix: add x\n\nbody\n\nSigned-off-by: A User <a@b.com>")
+        argv = [
+            "cg",
+            "--message-file",
+            str(f),
+            "--disable",
+            "signature,imperative",
+            "--min-description-length",
+            "3",
+        ]
+        with (
+            patch("sys.argv", argv),
+            patch(
+                "git_commit_guard._load_config",
+                return_value={"min-description-length": 6},
+            ),
+        ):
+            assert main() == 0
+
     def test_types_cli_overrides_config(self, tmp_path):
         f = tmp_path / "msg"
         f.write_text("wip: add thing\n\nbody\n\nSigned-off-by: A User <a@b.com>")