sha1_name: convert get_sha1* to get_oid*

Now that all the callers of get_sha1 directly or indirectly use struct
object_id, rename the functions starting with get_sha1 to start with
get_oid.  Convert the internals in sha1_name.c to use struct object_id
as well, and eliminate explicit length checks where possible.  Convert a
use of 40 in get_oid_basic to GIT_SHA1_HEXSZ.

Outside of sha1_name.c and cache.h, this transition was made with the
following semantic patch:

@@
expression E1, E2;
@@
- get_sha1(E1, E2.hash)
+ get_oid(E1, &E2)

@@
expression E1, E2;
@@
- get_sha1(E1, E2->hash)
+ get_oid(E1, E2)

@@
expression E1, E2;
@@
- get_sha1_committish(E1, E2.hash)
+ get_oid_committish(E1, &E2)

@@
expression E1, E2;
@@
- get_sha1_committish(E1, E2->hash)
+ get_oid_committish(E1, E2)

@@
expression E1, E2;
@@
- get_sha1_treeish(E1, E2.hash)
+ get_oid_treeish(E1, &E2)

@@
expression E1, E2;
@@
- get_sha1_treeish(E1, E2->hash)
+ get_oid_treeish(E1, E2)

@@
expression E1, E2;
@@
- get_sha1_commit(E1, E2.hash)
+ get_oid_commit(E1, &E2)

@@
expression E1, E2;
@@
- get_sha1_commit(E1, E2->hash)
+ get_oid_commit(E1, E2)

@@
expression E1, E2;
@@
- get_sha1_tree(E1, E2.hash)
+ get_oid_tree(E1, &E2)

@@
expression E1, E2;
@@
- get_sha1_tree(E1, E2->hash)
+ get_oid_tree(E1, E2)

@@
expression E1, E2;
@@
- get_sha1_blob(E1, E2.hash)
+ get_oid_blob(E1, &E2)

@@
expression E1, E2;
@@
- get_sha1_blob(E1, E2->hash)
+ get_oid_blob(E1, E2)

@@
expression E1, E2, E3, E4;
@@
- get_sha1_with_context(E1, E2, E3.hash, E4)
+ get_oid_with_context(E1, E2, &E3, E4)

@@
expression E1, E2, E3, E4;
@@
- get_sha1_with_context(E1, E2, E3->hash, E4)
+ get_oid_with_context(E1, E2, E3, E4)

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

commit.c

@@ -59,7 +59,7 @@ struct commit *lookup_commit_reference_by_name(const char *name)
 	struct object_id oid;
 	struct commit *commit;
 
-	if (get_sha1_committish(name, oid.hash))
+	if (get_oid_committish(name, &oid))
 		return NULL;
 	commit = lookup_commit_reference(&oid);
 	if (parse_commit(commit))
@@ -1587,7 +1587,7 @@ struct commit *get_merge_parent(const char *name)
 	struct object *obj;
 	struct commit *commit;
 	struct object_id oid;
-	if (get_sha1(name, oid.hash))
+	if (get_oid(name, &oid))
 		return NULL;
 	obj = parse_object(&oid);
 	commit = (struct commit *)peel_to_type(name, 0, obj, OBJ_COMMIT);