Merge branch 'jk/ambiguous-short-object-names'

When given an abbreviated object name that is not (or more
realistically, "no longer") unique, we gave a fatal error
"ambiguous argument".  This error is now accompanied by hints that
lists the objects that begins with the given prefix.  During the
course of development of this new feature, numerous minor bugs were
uncovered and corrected, the most notable one of which is that we
gave "short SHA1 xxxx is ambiguous." twice without good reason.

* jk/ambiguous-short-object-names:
  get_short_sha1: make default disambiguation configurable
  get_short_sha1: list ambiguous objects on error
  for_each_abbrev: drop duplicate objects
  sha1_array: let callbacks interrupt iteration
  get_short_sha1: mark ambiguity error for translation
  get_short_sha1: NUL-terminate hex prefix
  get_short_sha1: refactor init of disambiguation code
  get_short_sha1: parse tags when looking for treeish
  get_sha1: propagate flags to child functions
  get_sha1: avoid repeating ourselves via ONLY_TO_DIE
  get_sha1: detect buggy calls with multiple disambiguators

Author: gitster

Documentation/technical/api-sha1-array.txt

@@ -38,16 +38,20 @@ Functions
 `sha1_array_for_each_unique`::
 	Efficiently iterate over each unique element of the list,
 	executing the callback function for each one. If the array is
-	not sorted, this function has the side effect of sorting it.
+	not sorted, this function has the side effect of sorting it. If
+	the callback returns a non-zero value, the iteration ends
+	immediately and the callback's return is propagated; otherwise,
+	0 is returned.
 
 Examples
 --------
 
 -----------------------------------------
-void print_callback(const unsigned char sha1[20],
+int print_callback(const unsigned char sha1[20],
 		    void *data)
 {
 	printf("%s\n", sha1_to_hex(sha1));
+	return 0; /* always continue */
 }
 
 void some_func(void)

builtin/cat-file.c

@@ -401,11 +401,12 @@ struct object_cb_data {
 	struct expand_data *expand;
 };
 
-static void batch_object_cb(const unsigned char sha1[20], void *vdata)
+static int batch_object_cb(const unsigned char sha1[20], void *vdata)
 {
 	struct object_cb_data *data = vdata;
 	hashcpy(data->expand->oid.hash, sha1);
 	batch_object_write(NULL, data->opt, data->expand);
+	return 0;
 }
 
 static int batch_loose_object(const unsigned char *sha1,

builtin/receive-pack.c

@@ -268,9 +268,10 @@ static int show_ref_cb(const char *path_full, const struct object_id *oid,
 	return 0;
 }
 
-static void show_one_alternate_sha1(const unsigned char sha1[20], void *unused)
+static int show_one_alternate_sha1(const unsigned char sha1[20], void *unused)
 {
 	show_ref(".have", sha1);
+	return 0;
 }
 
 static void collect_one_alternate_ref(const struct ref *ref, void *data)

cache.h

@@ -1206,6 +1206,11 @@ struct object_context {
 #define GET_SHA1_FOLLOW_SYMLINKS 0100
 #define GET_SHA1_ONLY_TO_DIE    04000
 
+#define GET_SHA1_DISAMBIGUATORS \
+	(GET_SHA1_COMMIT | GET_SHA1_COMMITTISH | \
+	GET_SHA1_TREE | GET_SHA1_TREEISH | \
+	GET_SHA1_BLOB)
+
 extern int get_sha1(const char *str, unsigned char *sha1);
 extern int get_sha1_commit(const char *str, unsigned char *sha1);
 extern int get_sha1_committish(const char *str, unsigned char *sha1);
@@ -1220,6 +1225,8 @@ extern int get_oid(const char *str, struct object_id *oid);
 typedef int each_abbrev_fn(const unsigned char *sha1, void *);
 extern int for_each_abbrev(const char *prefix, each_abbrev_fn, void *);
 
+extern int set_disambiguate_hint_config(const char *var, const char *value);
+
 /*
  * Try to read a SHA1 in hexadecimal format from the 40 characters
  * starting at hex.  Write the 20-byte result to sha1 in binary form.

config.c

@@ -841,6 +841,9 @@ static int git_default_core_config(const char *var, const char *value)
 		return 0;
 	}
 
+	if (!strcmp(var, "core.disambiguate"))
+		return set_disambiguate_hint_config(var, value);
+
 	if (!strcmp(var, "core.loosecompression")) {
 		int level = git_config_int(var, value);
 		if (level == -1)

sha1-array.c

@@ -42,7 +42,7 @@ void sha1_array_clear(struct sha1_array *array)
 	array->sorted = 0;
 }
 
-void sha1_array_for_each_unique(struct sha1_array *array,
+int sha1_array_for_each_unique(struct sha1_array *array,
 				for_each_sha1_fn fn,
 				void *data)
 {
@@ -52,8 +52,12 @@ void sha1_array_for_each_unique(struct sha1_array *array,
 		sha1_array_sort(array);
 
 	for (i = 0; i < array->nr; i++) {
+		int ret;
 		if (i > 0 && !hashcmp(array->sha1[i], array->sha1[i-1]))
 			continue;
-		fn(array->sha1[i], data);
+		ret = fn(array->sha1[i], data);
+		if (ret)
+			return ret;
 	}
+	return 0;
 }

sha1-array.h

@@ -14,10 +14,10 @@ void sha1_array_append(struct sha1_array *array, const unsigned char *sha1);
 int sha1_array_lookup(struct sha1_array *array, const unsigned char *sha1);
 void sha1_array_clear(struct sha1_array *array);
 
-typedef void (*for_each_sha1_fn)(const unsigned char sha1[20],
-				 void *data);
-void sha1_array_for_each_unique(struct sha1_array *array,
-				for_each_sha1_fn fn,
+typedef int (*for_each_sha1_fn)(const unsigned char sha1[20],
 				void *data);
+int sha1_array_for_each_unique(struct sha1_array *array,
+			       for_each_sha1_fn fn,
+			       void *data);
 
 #endif /* SHA1_ARRAY_H */