Do not print 'dangling' for cat-file in case of ambiguity

The return values -1 and -2 from get_oid could mean two different
things, depending on whether they were from an enum returned by
get_tree_entry_follow_symlinks, or from a different code path.  This
caused 'dangling' to be printed from a git cat-file in the case of an
ambiguous (-2) result.

Unify the results of get_oid* and get_tree_entry_follow_symlinks to be
one common type, with unambiguous values.

Signed-off-by: David Turner <novalis@novalis.org>
Reported-by: Eric Wong <e@80x24.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-cat-file.txt

@@ -252,6 +252,12 @@ the repository, then `cat-file` will ignore any custom format and print:
 <object> SP missing LF
 ------------
 
+If a name is specified that might refer to more than one object (an ambiguous short sha), then `cat-file` will ignore any custom format and print:
+
+------------
+<object> SP ambiguous LF
+------------
+
 If --follow-symlinks is used, and a symlink in the repository points
 outside the repository, then `cat-file` will ignore any custom format
 and print:

builtin/cat-file.c

@@ -380,7 +380,7 @@ static void batch_one_object(const char *obj_name,
 {
 	struct object_context ctx;
 	int flags = opt->follow_symlinks ? GET_OID_FOLLOW_SYMLINKS : 0;
-	enum follow_symlinks_result result;
+	enum get_oid_result result;
 
 	result = get_oid_with_context(obj_name, flags, &data->oid, &ctx);
 	if (result != FOUND) {
@@ -388,6 +388,9 @@ static void batch_one_object(const char *obj_name,
 		case MISSING_OBJECT:
 			printf("%s missing\n", obj_name);
 			break;
+		case SHORT_NAME_AMBIGUOUS:
+			printf("%s ambiguous\n", obj_name);
+			break;
 		case DANGLING_SYMLINK:
 			printf("dangling %"PRIuMAX"\n%s\n",
 			       (uintmax_t)strlen(obj_name), obj_name);

cache.h

@@ -1332,6 +1332,24 @@ struct object_context {
 	GET_OID_TREE | GET_OID_TREEISH | \
 	GET_OID_BLOB)
 
+enum get_oid_result {
+	FOUND = 0,
+	MISSING_OBJECT = -1, /* The requested object is missing */
+	SHORT_NAME_AMBIGUOUS = -2,
+	/* The following only apply when symlinks are followed */
+	DANGLING_SYMLINK = -4, /*
+				* The initial symlink is there, but
+				* (transitively) points to a missing
+				* in-tree file
+				*/
+	SYMLINK_LOOP = -5,
+	NOT_DIR = -6, /*
+		       * Somewhere along the symlink chain, a path is
+		       * requested which contains a file as a
+		       * non-final element.
+		       */
+};
+
 extern int get_oid(const char *str, struct object_id *oid);
 extern int get_oid_commit(const char *str, struct object_id *oid);
 extern int get_oid_committish(const char *str, struct object_id *oid);
@@ -1339,7 +1357,7 @@ extern int get_oid_tree(const char *str, struct object_id *oid);
 extern int get_oid_treeish(const char *str, struct object_id *oid);
 extern int get_oid_blob(const char *str, struct object_id *oid);
 extern void maybe_die_on_misspelt_object_name(const char *name, const char *prefix);
-extern int get_oid_with_context(const char *str, unsigned flags, struct object_id *oid, struct object_context *oc);
+extern enum get_oid_result get_oid_with_context(const char *str, unsigned flags, struct object_id *oid, struct object_context *oc);
 
 
 typedef int each_abbrev_fn(const struct object_id *oid, void *);

sha1-name.c

@@ -190,9 +190,6 @@ static void find_short_packed_object(struct disambiguate_state *ds)
 		unique_in_pack(p, ds);
 }
 
-#define SHORT_NAME_NOT_FOUND (-1)
-#define SHORT_NAME_AMBIGUOUS (-2)
-
 static int finish_object_disambiguation(struct disambiguate_state *ds,
 					struct object_id *oid)
 {
@@ -200,7 +197,7 @@ static int finish_object_disambiguation(struct disambiguate_state *ds,
 		return SHORT_NAME_AMBIGUOUS;
 
 	if (!ds->candidate_exists)
-		return SHORT_NAME_NOT_FOUND;
+		return MISSING_OBJECT;
 
 	if (!ds->candidate_checked)
 		/*
@@ -414,8 +411,9 @@ static int sort_ambiguous(const void *a, const void *b)
 	return a_type_sort > b_type_sort ? 1 : -1;
 }
 
-static int get_short_oid(const char *name, int len, struct object_id *oid,
-			  unsigned flags)
+static enum get_oid_result get_short_oid(const char *name, int len,
+					 struct object_id *oid,
+					 unsigned flags)
 {
 	int status;
 	struct disambiguate_state ds;
@@ -733,7 +731,7 @@ static inline int push_mark(const char *string, int len)
 	return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
 }
 
-static int get_oid_1(const char *name, int len, struct object_id *oid, unsigned lookup_flags);
+static enum get_oid_result get_oid_1(const char *name, int len, struct object_id *oid, unsigned lookup_flags);
 static int interpret_nth_prior_checkout(const char *name, int namelen, struct strbuf *buf);
 
 static int get_oid_basic(const char *str, int len, struct object_id *oid,
@@ -883,11 +881,12 @@ static int get_oid_basic(const char *str, int len, struct object_id *oid,
 	return 0;
 }
 
-static int get_parent(const char *name, int len,
-		      struct object_id *result, int idx)
+static enum get_oid_result get_parent(const char *name, int len,
+				      struct object_id *result, int idx)
 {
 	struct object_id oid;
-	int ret = get_oid_1(name, len, &oid, GET_OID_COMMITTISH);
+	enum get_oid_result ret = get_oid_1(name, len, &oid,
+					    GET_OID_COMMITTISH);
 	struct commit *commit;
 	struct commit_list *p;
 
@@ -895,24 +894,25 @@ static int get_parent(const char *name, int len,
 		return ret;
 	commit = lookup_commit_reference(the_repository, &oid);
 	if (parse_commit(commit))
-		return -1;
+		return MISSING_OBJECT;
 	if (!idx) {
 		oidcpy(result, &commit->object.oid);
-		return 0;
+		return FOUND;
 	}
 	p = commit->parents;
 	while (p) {
 		if (!--idx) {
 			oidcpy(result, &p->item->object.oid);
-			return 0;
+			return FOUND;
 		}
 		p = p->next;
 	}
-	return -1;
+	return MISSING_OBJECT;
 }
 
-static int get_nth_ancestor(const char *name, int len,
-			    struct object_id *result, int generation)
+static enum get_oid_result get_nth_ancestor(const char *name, int len,
+					    struct object_id *result,
+					    int generation)
 {
 	struct object_id oid;
 	struct commit *commit;
@@ -923,15 +923,15 @@ static int get_nth_ancestor(const char *name, int len,
 		return ret;
 	commit = lookup_commit_reference(the_repository, &oid);
 	if (!commit)
-		return -1;
+		return MISSING_OBJECT;
 
 	while (generation--) {
 		if (parse_commit(commit) || !commit->parents)
-			return -1;
+			return MISSING_OBJECT;
 		commit = commit->parents->item;
 	}
 	oidcpy(result, &commit->object.oid);
-	return 0;
+	return FOUND;
 }
 
 struct object *peel_to_type(const char *name, int namelen,
@@ -1077,7 +1077,9 @@ static int get_describe_name(const char *name, int len, struct object_id *oid)
 	return -1;
 }
 
-static int get_oid_1(const char *name, int len, struct object_id *oid, unsigned lookup_flags)
+static enum get_oid_result get_oid_1(const char *name, int len,
+				     struct object_id *oid,
+				     unsigned lookup_flags)
 {
 	int ret, has_suffix;
 	const char *cp;
@@ -1111,16 +1113,16 @@ static int get_oid_1(const char *name, int len, struct object_id *oid, unsigned
 
 	ret = peel_onion(name, len, oid, lookup_flags);
 	if (!ret)
-		return 0;
+		return FOUND;
 
 	ret = get_oid_basic(name, len, oid, lookup_flags);
 	if (!ret)
-		return 0;
+		return FOUND;
 
 	/* It could be describe output that is "SOMETHING-gXXXX" */
 	ret = get_describe_name(name, len, oid);
 	if (!ret)
-		return 0;
+		return FOUND;
 
 	return get_short_oid(name, len, oid, lookup_flags);
 }
@@ -1664,11 +1666,11 @@ static char *resolve_relative_path(const char *rel)
 			   rel);
 }
 
-static int get_oid_with_context_1(const char *name,
-				  unsigned flags,
-				  const char *prefix,
-				  struct object_id *oid,
-				  struct object_context *oc)
+static enum get_oid_result get_oid_with_context_1(const char *name,
+						  unsigned flags,
+						  const char *prefix,
+						  struct object_id *oid,
+						  struct object_context *oc)
 {
 	int ret, bracket_depth;
 	int namelen = strlen(name);

tree-walk.c

@@ -579,10 +579,10 @@ int get_tree_entry(const struct object_id *tree_oid, const char *name, struct ob
  * with the sha1 of the found object, and *mode will hold the mode of
  * the object.
  *
- * See the code for enum follow_symlink_result for a description of
+ * See the code for enum get_oid_result for a description of
  * the return values.
  */
-enum follow_symlinks_result get_tree_entry_follow_symlinks(struct object_id *tree_oid, const char *name, struct object_id *result, struct strbuf *result_path, unsigned *mode)
+enum get_oid_result get_tree_entry_follow_symlinks(struct object_id *tree_oid, const char *name, struct object_id *result, struct strbuf *result_path, unsigned *mode)
 {
 	int retval = MISSING_OBJECT;
 	struct dir_state *parents = NULL;

tree-walk.h

@@ -51,23 +51,7 @@ struct traverse_info;
 typedef int (*traverse_callback_t)(int n, unsigned long mask, unsigned long dirmask, struct name_entry *entry, struct traverse_info *);
 int traverse_trees(struct index_state *istate, int n, struct tree_desc *t, struct traverse_info *info);
 
-enum follow_symlinks_result {
-	FOUND = 0, /* This includes out-of-tree links */
-	MISSING_OBJECT = -1, /* The initial symlink is missing */
-	DANGLING_SYMLINK = -2, /*
-				* The initial symlink is there, but
-				* (transitively) points to a missing
-				* in-tree file
-				*/
-	SYMLINK_LOOP = -3,
-	NOT_DIR = -4, /*
-		       * Somewhere along the symlink chain, a path is
-		       * requested which contains a file as a
-		       * non-final element.
-		       */
-};
-
-enum follow_symlinks_result get_tree_entry_follow_symlinks(struct object_id *tree_oid, const char *name, struct object_id *result, struct strbuf *result_path, unsigned *mode);
+enum get_oid_result get_tree_entry_follow_symlinks(struct object_id *tree_oid, const char *name, struct object_id *result, struct strbuf *result_path, unsigned *mode);
 
 struct traverse_info {
 	const char *traverse_path;