manifest: reject lines shorter than 42 bytes, not 22

Yuya correctly spotted during the review of f27f8e9ef1e73 that we're
dealing with hexlified hashes here, and so it should be 42 bytes not
22.

Differential Revision: https://phab.mercurial-scm.org/D5347

mercurial/cext/manifest.c

@@ -127,11 +127,11 b' static int find_lines(lazymanifest *self'
 		if (!next) {
 			return MANIFEST_MALFORMED;
 		}
-		if ((next - data) < 22) {
-			/* We should have at least 22 bytes in a line:
+		if ((next - data) < 42) {
+			/* We should have at least 42 bytes in a line:
 			   1 byte filename
 			   1 NUL
-			   20 bytes of hash
+			   40 bytes of hash
 			   so we can give up here.
 			*/
 			return MANIFEST_TOO_SHORT_LINE;