ref-filter: modify "%(objectname:short)" to take length

Add support for %(objectname:short,<length>) which would print the
abbreviated unique objectname of given length. When no length is
specified 7 is used. The minimum length is 4.

Add tests and documentation for the same.

Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

3 files changed, 55 insertions, 8 deletions

diff --git a/Documentation/git-for-each-ref.txt b/Documentation/git-for-each-ref.txt
index 6a476ba6b4..5097915a97 100644
--- a/Documentation/git-for-each-ref.txt
+++ b/Documentation/git-for-each-ref.txt
@@ -103,6 +103,8 @@ objectsize::
 objectname::
 	The object name (aka SHA-1).
 	For a non-ambiguous abbreviation of the object name append `:short`.
+	The length can be explicitly specified by appending either
+	`:short,<length>` or `:<length>,short`.  Minimum length is 4.
 
 upstream::
 	The name of a local ref which can be considered ``upstream''
diff --git a/ref-filter.c b/ref-filter.c
index b0e86ae32d..223daeb06b 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -454,14 +454,37 @@ static void *get_obj(const unsigned char *sha1, struct object **obj, unsigned lo
 static int grab_objectname(const char *name, const unsigned char *sha1,
 			    struct atom_value *v)
 {
-	if (!strcmp(name, "objectname")) {
-		char *s = xmalloc(41);
-		strcpy(s, sha1_to_hex(sha1));
-		v->s = s;
-		return 1;
-	}
-	if (!strcmp(name, "objectname:short")) {
-		v->s = xstrdup(find_unique_abbrev(sha1, DEFAULT_ABBREV));
+	const char *p;
+
+	if (match_atom_name(name, "objectname", &p)) {
+		struct strbuf **s, **to_free;
+		int length = DEFAULT_ABBREV;
+
+		/*  No arguments given, copy the entire objectname */
+		if (!p) {
+			char *s = xmalloc(41);
+			strcpy(s, sha1_to_hex(sha1));
+			v->s = s;
+		} else {
+			s = to_free = strbuf_split_str(p, ',', 0);
+			while (*s) {
+				/*  Strip trailing comma */
+				if (s[1])
+					strbuf_setlen(s[0], s[0]->len - 1);
+				if (!strtoul_ui(s[0]->buf, 10, (unsigned int *)&length))
+					;
+				/*  The `short` argument uses the default length */
+				else if (!strcmp("short", s[0]->buf))
+					;
+				else
+					die(_("format: unknown option entered with objectname:%s"), s[0]->buf);
+				s++;
+			}
+			if (length < MINIMUM_ABBREV)
+				length = MINIMUM_ABBREV;
+			v->s = xstrdup(find_unique_abbrev(sha1, length));
+			free(to_free);
+		}
 		return 1;
 	}
 	return 0;
diff --git a/t/t6300-for-each-ref.sh b/t/t6300-for-each-ref.sh
index 7c9bec7630..7f675d279c 100755
--- a/t/t6300-for-each-ref.sh
+++ b/t/t6300-for-each-ref.sh
@@ -385,6 +385,28 @@ test_expect_success 'Check short objectname format' '
 	test_cmp expected actual
 '
 
+cat >expected <<EOF
+$(git rev-parse --short=1 HEAD)
+EOF
+
+test_expect_success 'Check objectname:short format when size is less than MINIMUM_ABBREV' '
+	git for-each-ref --format="%(objectname:short,1)" refs/heads >actual &&
+	test_cmp expected actual
+'
+
+cat >expected <<EOF
+$(git rev-parse --short=10 HEAD)
+EOF
+
+test_expect_success 'Check objectname:short format' '
+	git for-each-ref --format="%(objectname:short,10)" refs/heads >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'Check objectname:short format for invalid input' '
+	test_must_fail git for-each-ref --format="%(objectname:short,-1)" refs/heads
+'
+
 test_expect_success 'Check for invalid refname format' '
 	test_must_fail git for-each-ref --format="%(refname:INVALID)"
 '