object-file: add a compat_oid_in parameter to write_object_file_flags

To create the proper signatures for commit objects both versions of
the commit object need to be generated and signed.  After that it is
a waste to throw away the work of generating the compatibility hash
so update write_object_file_flags to take a compatibility hash input
parameter that it can use to skip the work of generating the
compatability hash.

Update the places that don't generate the compatability hash to
pass NULL so it is easy to tell write_object_file_flags should
not attempt to use their compatability hash.

Signed-off-by: "Eric W. Biederman" <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: ebiederm

cache-tree.c

@@ -448,7 +448,7 @@ static int update_one(struct cache_tree *it,
 		hash_object_file(the_hash_algo, buffer.buf, buffer.len,
 				 OBJ_TREE, &it->oid);
 	} else if (write_object_file_flags(buffer.buf, buffer.len, OBJ_TREE,
-					   &it->oid, flags & WRITE_TREE_SILENT
+					   &it->oid, NULL, flags & WRITE_TREE_SILENT
 					   ? HASH_SILENT : 0)) {
 		strbuf_release(&buffer);
 		return -1;

object-file.c

@@ -2235,7 +2235,7 @@ int stream_loose_object(struct input_stream *in_stream, size_t len,
 
 int write_object_file_flags(const void *buf, unsigned long len,
 			    enum object_type type, struct object_id *oid,
-			    unsigned flags)
+			    struct object_id *compat_oid_in, unsigned flags)
 {
 	struct repository *repo = the_repository;
 	const struct git_hash_algo *algo = repo->hash_algo;
@@ -2246,7 +2246,9 @@ int write_object_file_flags(const void *buf, unsigned long len,
 
 	/* Generate compat_oid */
 	if (compat) {
-		if (type == OBJ_BLOB)
+		if (compat_oid_in)
+			oidcpy(&compat_oid, compat_oid_in);
+		else if (type == OBJ_BLOB)
 			hash_object_file(compat, buf, len, type, &compat_oid);
 		else {
 			struct strbuf converted = STRBUF_INIT;

object-store-ll.h

@@ -255,11 +255,11 @@ void hash_object_file(const struct git_hash_algo *algo, const void *buf,
 
 int write_object_file_flags(const void *buf, unsigned long len,
 			    enum object_type type, struct object_id *oid,
-			    unsigned flags);
+			    struct object_id *comapt_oid_in, unsigned flags);
 static inline int write_object_file(const void *buf, unsigned long len,
 				    enum object_type type, struct object_id *oid)
 {
-	return write_object_file_flags(buf, len, type, oid, 0);
+	return write_object_file_flags(buf, len, type, oid, NULL, 0);
 }
 
 int write_object_file_literally(const void *buf, unsigned long len,