This is mostly cosmetic.  it doesn't cause any practical harm on sha256
repos.  Since we hardcode the sha1 digest length (which should be
_STRING too...) we just truncate the object id in some cases, which in
turns means we have to search for a matching object.

Since we don't know in this libexec the object format, and this is just
an hint anyway[*], let's drop the pedantic check.

ok?

[*]: i'm considering to change how the merge strategy works so that if
     we fail to patch the provided blob, we retry using the local file
     instead.  This will also fix some strange error messages like the
     one Lucas hit by manually editing a patch.

diff /home/op/w/got
commit - d9048d75a8da25621fe5e1facf2b6923258311a3
path + /home/op/w/got
blob - 9b5c6b818d19c41eb3e9e4ffede13cd4a6fb81f5
file + libexec/got-read-patch/got-read-patch.c
--- libexec/got-read-patch/got-read-patch.c
+++ libexec/got-read-patch/got-read-patch.c
@@ -184,7 +184,6 @@ filexbit(const char *line)
 static const struct got_error *
 blobid(const char *line, char **blob, int git)
 {
-	uint8_t digest[SHA1_DIGEST_LENGTH];
 	size_t len;
 
 	*blob = NULL;
@@ -193,11 +192,6 @@ blobid(const char *line, char **blob, int git)
 	if ((*blob = strndup(line, len)) == NULL)
 		return got_error_from_errno("strndup");
 
-	if (!git && !got_parse_hash_digest(digest, *blob, GOT_HASH_SHA1)) {
-		/* silently ignore invalid blob ids */
-		free(*blob);
-		*blob = NULL;
-	}
 	return NULL;
 }