config: handle malformed git submodules (#1224)

A git submodule needs two items in its config: url to clone from, path
to clone to. If either is missing, core git simply ignores this
submodule entry. Dulwich should do the same.

dulwich/config.py

@@ -780,9 +780,15 @@ def parse_submodules(config: ConfigFile) -> Iterator[Tuple[bytes, bytes, bytes]]
     for section in config.keys():
         section_kind, section_name = section
         if section_kind == b"submodule":
-            sm_path = config.get(section, b"path")
-            sm_url = config.get(section, b"url")
-            yield (sm_path, sm_url, section_name)
+            try:
+                sm_path = config.get(section, b"path")
+                sm_url = config.get(section, b"url")
+                yield (sm_path, sm_url, section_name)
+            except KeyError:
+                # If either path or url is missing, just ignore this
+                # submodule entry and move on to the next one. This is
+                # how git itself handles malformed .gitmodule entries.
+                pass
 
 
 def iter_instead_of(config: Config, push: bool = False) -> Iterable[Tuple[str, str]]:

dulwich/tests/test_config.py

@@ -423,6 +423,31 @@ class SubmodulesTests(TestCase):
 [submodule "core/lib"]
 \tpath = core/lib
 \turl = https://github.com/phhusson/QuasselC.git
+"""
+            )
+        )
+        got = list(parse_submodules(cf))
+        self.assertEqual(
+            [
+                (
+                    b"core/lib",
+                    b"https://github.com/phhusson/QuasselC.git",
+                    b"core/lib",
+                )
+            ],
+            got,
+        )
+
+    def testMalformedSubmodules(self):
+        cf = ConfigFile.from_file(
+            BytesIO(
+                b"""\
+[submodule "core/lib"]
+\tpath = core/lib
+\turl = https://github.com/phhusson/QuasselC.git
+
+[submodule "dulwich"]
+\turl = https://github.com/jelmer/dulwich
 """
             )
         )