Convert lookup_commit* to struct object_id

Convert lookup_commit, lookup_commit_or_die,
lookup_commit_reference, and lookup_commit_reference_gently to take
struct object_id arguments.

Introduce a temporary in parse_object buffer in order to convert this
function.  This is required since in order to convert parse_object and
parse_object_buffer, lookup_commit_reference_gently and
lookup_commit_or_die would need to be converted.  Not introducing a
temporary would therefore require that lookup_commit_or_die take a
struct object_id *, but lookup_commit would take unsigned char *,
leaving a confusing and hard-to-use interface.

parse_object_buffer will lose this temporary in a later patch.

This commit was created with manual changes to commit.c, commit.h, and
object.c, plus the following semantic patch:

@@
expression E1, E2;
@@
- lookup_commit_reference_gently(E1.hash, E2)
+ lookup_commit_reference_gently(&E1, E2)

@@
expression E1, E2;
@@
- lookup_commit_reference_gently(E1->hash, E2)
+ lookup_commit_reference_gently(E1, E2)

@@
expression E1;
@@
- lookup_commit_reference(E1.hash)
+ lookup_commit_reference(&E1)

@@
expression E1;
@@
- lookup_commit_reference(E1->hash)
+ lookup_commit_reference(E1)

@@
expression E1;
@@
- lookup_commit(E1.hash)
+ lookup_commit(&E1)

@@
expression E1;
@@
- lookup_commit(E1->hash)
+ lookup_commit(E1)

@@
expression E1, E2;
@@
- lookup_commit_or_die(E1.hash, E2)
+ lookup_commit_or_die(&E1, E2)

@@
expression E1, E2;
@@
- lookup_commit_or_die(E1->hash, E2)
+ lookup_commit_or_die(E1, E2)

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

commit.h

@@ -45,18 +45,18 @@ enum decoration_type {
 void add_name_decoration(enum decoration_type type, const char *name, struct object *obj);
 const struct name_decoration *get_name_decoration(const struct object *obj);
 
-struct commit *lookup_commit(const unsigned char *sha1);
-struct commit *lookup_commit_reference(const unsigned char *sha1);
-struct commit *lookup_commit_reference_gently(const unsigned char *sha1,
+struct commit *lookup_commit(const struct object_id *oid);
+struct commit *lookup_commit_reference(const struct object_id *oid);
+struct commit *lookup_commit_reference_gently(const struct object_id *oid,
 					      int quiet);
 struct commit *lookup_commit_reference_by_name(const char *name);
 
 /*
- * Look up object named by "sha1", dereference tag as necessary,
- * get a commit and return it. If "sha1" does not dereference to
+ * Look up object named by "oid", dereference tag as necessary,
+ * get a commit and return it. If "oid" does not dereference to
  * a commit, use ref_name to report an error and die.
  */
-struct commit *lookup_commit_or_die(const unsigned char *sha1, const char *ref_name);
+struct commit *lookup_commit_or_die(const struct object_id *oid, const char *ref_name);
 
 int parse_commit_buffer(struct commit *item, const void *buffer, unsigned long size);
 int parse_commit_gently(struct commit *item, int quiet_on_missing);