Merge branch 'jc/sha1-name-object-peeler'

There was no good way to ask "I have a random string that came from
outside world. I want to turn it into a 40-hex object name while
making sure such an object exists".  A new peeling suffix ^{object}
can be used for that purpose, together with "rev-parse --verify".

* jc/sha1-name-object-peeler:
  peel_onion(): teach $foo^{object} peeler
  peel_onion: disambiguate to favor tree-ish when we know we want a tree-ish

Documentation/revisions.txt

@@ -116,6 +116,11 @@ some output processing may assume ref names in UTF-8.
   object of that type is found or the object cannot be
   dereferenced anymore (in which case, barf).  '<rev>{caret}0'
   is a short-hand for '<rev>{caret}\{commit\}'.
++
+'rev{caret}\{object\}' can be used to make sure 'rev' names an
+object that exists, without requiring 'rev' to be a tag, and
+without dereferencing 'rev'; because a tag is already an object,
+it does not have to be dereferenced even once to get to an object.
 
 '<rev>{caret}\{\}', e.g. 'v0.99.8{caret}\{\}'::
   A suffix '{caret}' followed by an empty brace pair

sha1_name.c

@@ -594,7 +594,7 @@ struct object *peel_to_type(const char *name, int namelen,
 	while (1) {
 		if (!o || (!o->parsed && !parse_object(o->sha1)))
 			return NULL;
-		if (o->type == expected_type)
+		if (expected_type == OBJ_ANY || o->type == expected_type)
 			return o;
 		if (o->type == OBJ_TAG)
 			o = ((struct tag*) o)->tagged;
@@ -645,6 +645,8 @@ static int peel_onion(const char *name, int len, unsigned char *sha1)
 		expected_type = OBJ_TREE;
 	else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')
 		expected_type = OBJ_BLOB;
+	else if (!prefixcmp(sp, "object}"))
+		expected_type = OBJ_ANY;
 	else if (sp[0] == '}')
 		expected_type = OBJ_NONE;
 	else if (sp[0] == '/')
@@ -654,6 +656,8 @@ static int peel_onion(const char *name, int len, unsigned char *sha1)
 
 	if (expected_type == OBJ_COMMIT)
 		lookup_flags = GET_SHA1_COMMITTISH;
+	else if (expected_type == OBJ_TREE)
+		lookup_flags = GET_SHA1_TREEISH;
 
 	if (get_sha1_1(name, sp - name - 2, outer, lookup_flags))
 		return -1;