fsck: split ".gitmodules too large" error from parse failure

Since ed8b10f (fsck: check .gitmodules content,
2018-05-02), we'll report a gitmodulesParse error for two
conditions:

  - a .gitmodules entry is not syntactically valid

  - a .gitmodules entry is larger than core.bigFileThreshold

with the intent that we can detect malicious files and
protect downstream clients. E.g., from the issue in
0383bbb (submodule-config: verify submodule names as
paths, 2018-04-30).

But these conditions are actually quite different with
respect to that bug:

 - a syntactically invalid file cannot trigger the problem,
   as the victim would barf before hitting the problematic
   code

 - a too-big .gitmodules _can_ trigger the problem. Even
   though it is obviously silly to have a 500MB .gitmodules
   file, the submodule code will happily parse it if you
   have enough memory.

So it may be reasonable to configure their severity
separately. Let's add a new class for the "too large" case
to allow that.

Signed-off-by: Jeff King <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: peff

fsck.c

@@ -63,6 +63,7 @@ static struct oidset gitmodules_done = OIDSET_INIT;
 	FUNC(GITMODULES_MISSING, ERROR) \
 	FUNC(GITMODULES_BLOB, ERROR) \
 	FUNC(GITMODULES_PARSE, ERROR) \
+	FUNC(GITMODULES_LARGE, ERROR) \
 	FUNC(GITMODULES_NAME, ERROR) \
 	FUNC(GITMODULES_SYMLINK, ERROR) \
 	/* warnings */ \
@@ -1005,7 +1006,7 @@ static int fsck_blob(struct blob *blob, const char *buf,
 		 * that an error.
 		 */
 		return report(options, &blob->object,
-			      FSCK_MSG_GITMODULES_PARSE,
+			      FSCK_MSG_GITMODULES_LARGE,
 			      ".gitmodules too large to parse");
 	}