describe: fix --no-exact-match

Since 2c33f75 (Teach git-describe --exact-match to avoid expensive
tag searches, 2008-02-24) git describe accepts --no-exact-match, but it
does the same as --exact-match, an alias for --candidates=0.  That's
because it's defined using OPT_SET_INT with a value of 0, which sets 0
when negated as well.

Let --no-exact-match set the number of candidates to the default value
instead.  Users that need a more specific lack of exactitude can specify
their preferred value using --candidates, as before.

The "--no-exact-match" option was not covered in the tests, so let's
add a few.  Also add a case where --exact-match option is used on a
commit that cannot be described without distance from tags and make
sure the command fails.

Signed-off-by: René Scharfe <[email protected]>
[jc: added trivial tests]
Signed-off-by: Junio C Hamano <[email protected]>

Author: rscharfe

builtin/describe.c

@@ -24,6 +24,7 @@
 #include "commit-slab.h"
 
 #define MAX_TAGS	(FLAG_BITS - 1)
+#define DEFAULT_CANDIDATES 10
 
 define_commit_slab(commit_names, struct commit_name *);
 
@@ -40,7 +41,7 @@ static int tags;	/* Allow lightweight tags */
 static int longformat;
 static int first_parent;
 static int abbrev = -1; /* unspecified */
-static int max_candidates = 10;
+static int max_candidates = DEFAULT_CANDIDATES;
 static struct hashmap names;
 static int have_util;
 static struct string_list patterns = STRING_LIST_INIT_NODUP;
@@ -556,6 +557,15 @@ static void describe(const char *arg, int last_one)
 	strbuf_release(&sb);
 }
 
+static int option_parse_exact_match(const struct option *opt, const char *arg,
+				    int unset)
+{
+	BUG_ON_OPT_ARG(arg);
+
+	max_candidates = unset ? DEFAULT_CANDIDATES : 0;
+	return 0;
+}
+
 int cmd_describe(int argc, const char **argv, const char *prefix)
 {
 	int contains = 0;
@@ -567,8 +577,9 @@ int cmd_describe(int argc, const char **argv, const char *prefix)
 		OPT_BOOL(0, "long",       &longformat, N_("always use long format")),
 		OPT_BOOL(0, "first-parent", &first_parent, N_("only follow first parent")),
 		OPT__ABBREV(&abbrev),
-		OPT_SET_INT(0, "exact-match", &max_candidates,
-			    N_("only output exact matches"), 0),
+		OPT_CALLBACK_F(0, "exact-match", NULL, NULL,
+			       N_("only output exact matches"),
+			       PARSE_OPT_NOARG, option_parse_exact_match),
 		OPT_INTEGER(0, "candidates", &max_candidates,
 			    N_("consider <n> most recent tags (default: 10)")),
 		OPT_STRING_LIST(0, "match", &patterns, N_("pattern"),

t/t6120-describe.sh

@@ -85,6 +85,7 @@ check_describe e-1-gHASH --tags HEAD^^
 check_describe c-2-gHASH --tags HEAD^^2
 check_describe B --tags HEAD^^2^
 check_describe e --tags HEAD^^^
+check_describe e --tags --exact-match HEAD^^^
 
 check_describe heads/main --all HEAD
 check_describe tags/c-6-gHASH --all HEAD^
@@ -96,6 +97,13 @@ check_describe A-3-gHASH --long HEAD^^2
 check_describe c-7-gHASH --tags
 check_describe e-3-gHASH --first-parent --tags
 
+check_describe c-7-gHASH --tags --no-exact-match HEAD
+check_describe e-3-gHASH --first-parent --tags --no-exact-match HEAD
+
+test_expect_success '--exact-match failure' '
+	test_must_fail git describe --exact-match HEAD 2>err
+'
+
 test_expect_success 'describe --contains defaults to HEAD without commit-ish' '
 	echo "A^0" >expect &&
 	git checkout A &&