shorten_unambiguous_ref(): add strict mode

Add the strict mode of abbreviation to shorten_unambiguous_ref(), i.e. the
resulting ref won't trigger the ambiguous ref warning.

All users of shorten_unambiguous_ref() still use the loose mode.

Signed-off-by: Bert Wesarg <bert.wesarg@googlemail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-branch.c

@@ -311,14 +311,14 @@ static void fill_tracking_info(struct strbuf *stat, const char *branch_name,
 		if (branch && branch->merge && branch->merge[0]->dst &&
 		    show_upstream_ref)
 			strbuf_addf(stat, "[%s] ",
-			    shorten_unambiguous_ref(branch->merge[0]->dst));
+			    shorten_unambiguous_ref(branch->merge[0]->dst, 0));
 		return;
 	}
 
 	strbuf_addch(stat, '[');
 	if (show_upstream_ref)
 		strbuf_addf(stat, "%s: ",
-			shorten_unambiguous_ref(branch->merge[0]->dst));
+			shorten_unambiguous_ref(branch->merge[0]->dst, 0));
 	if (!ours)
 		strbuf_addf(stat, "behind %d] ", theirs);
 	else if (!theirs)

builtin-for-each-ref.c

@@ -601,7 +601,7 @@ static void populate_value(struct refinfo *ref)
 		if (formatp) {
 			formatp++;
 			if (!strcmp(formatp, "short"))
-				refname = shorten_unambiguous_ref(refname);
+				refname = shorten_unambiguous_ref(refname, 0);
 			else
 				die("unknown %.*s format %s",
 				    (int)(formatp - name), name, formatp);

refs.c

@@ -1681,7 +1681,7 @@ static void gen_scanf_fmt(char *scanf_fmt, const char *rule)
 	return;
 }
 
-char *shorten_unambiguous_ref(const char *ref)
+char *shorten_unambiguous_ref(const char *ref, int strict)
 {
 	int i;
 	static char **scanf_fmts;
@@ -1718,22 +1718,34 @@ char *shorten_unambiguous_ref(const char *ref)
 	/* skip first rule, it will always match */
 	for (i = nr_rules - 1; i > 0 ; --i) {
 		int j;
+		int rules_to_fail = i;
 		int short_name_len;
 
 		if (1 != sscanf(ref, scanf_fmts[i], short_name))
 			continue;
 
 		short_name_len = strlen(short_name);
 
+		/*
+		 * in strict mode, all (except the matched one) rules
+		 * must fail to resolve to a valid non-ambiguous ref
+		 */
+		if (strict)
+			rules_to_fail = nr_rules;
+
 		/*
 		 * check if the short name resolves to a valid ref,
 		 * but use only rules prior to the matched one
 		 */
-		for (j = 0; j < i; j++) {
+		for (j = 0; j < rules_to_fail; j++) {
 			const char *rule = ref_rev_parse_rules[j];
 			unsigned char short_objectname[20];
 			char refname[PATH_MAX];
 
+			/* skip matched rule */
+			if (i == j)
+				continue;
+
 			/*
 			 * the short name is ambiguous, if it resolves
 			 * (with this previous rule) to a valid ref
@@ -1749,7 +1761,7 @@ char *shorten_unambiguous_ref(const char *ref)
 		 * short name is non-ambiguous if all previous rules
 		 * haven't resolved to a valid ref
 		 */
-		if (j == i)
+		if (j == rules_to_fail)
 			return short_name;
 	}
 

refs.h

@@ -81,7 +81,7 @@ extern int for_each_reflog(each_ref_fn, void *);
 extern int check_ref_format(const char *target);
 
 extern const char *prettify_ref(const struct ref *ref);
-extern char *shorten_unambiguous_ref(const char *ref);
+extern char *shorten_unambiguous_ref(const char *ref, int strict);
 
 /** rename ref, return 0 on success **/
 extern int rename_ref(const char *oldref, const char *newref, const char *logmsg);