Add git_oid_nfmt - a flexible OID formatter

I frequently want to the the first N digits of an OID formatted
as a string and I'd like it to be efficient.  This function makes
that easy and I could rewrite the OID formatters in terms of it.

1 files changed, 38 insertions, 0 deletions

diff --git a/tests-clar/object/raw/convert.c b/tests-clar/object/raw/convert.c
index 74442c153..86f0d74a9 100644
--- a/tests-clar/object/raw/convert.c
+++ b/tests-clar/object/raw/convert.c
@@ -73,3 +73,41 @@ void test_object_raw_convert__succeed_on_oid_to_string_conversion_big(void)
 	cl_assert(str && str == big && *(str+GIT_OID_HEXSZ+2) == 'Y');
 	cl_assert(str && str == big && *(str+GIT_OID_HEXSZ+3) == 'Z');
 }
+
+static void check_partial_oid(
+	char *buffer, size_t count, const git_oid *oid, const char *expected)
+{
+	git_oid_nfmt(buffer, count, oid);
+	buffer[count] = '\0';
+	cl_assert_equal_s(expected, buffer);
+}
+
+void test_object_raw_convert__convert_oid_partially(void)
+{
+	const char *exp = "16a0123456789abcdef4b775213c23a8bd74f5e0";
+	git_oid in;
+	char big[GIT_OID_HEXSZ + 1 + 3]; /* note + 4 => big buffer */
+	char *str;
+
+	cl_git_pass(git_oid_fromstr(&in, exp));
+
+	git_oid_nfmt(big, sizeof(big), &in);
+	cl_assert_equal_s(exp, big);
+
+	git_oid_nfmt(big, GIT_OID_HEXSZ + 1, &in);
+	cl_assert_equal_s(exp, big);
+
+	check_partial_oid(big, 1, &in, "1");
+	check_partial_oid(big, 2, &in, "16");
+	check_partial_oid(big, 3, &in, "16a");
+	check_partial_oid(big, 4, &in, "16a0");
+	check_partial_oid(big, 5, &in, "16a01");
+
+	check_partial_oid(big, GIT_OID_HEXSZ, &in, exp);
+	check_partial_oid(
+		big, GIT_OID_HEXSZ - 1, &in, "16a0123456789abcdef4b775213c23a8bd74f5e");
+	check_partial_oid(
+		big, GIT_OID_HEXSZ - 2, &in, "16a0123456789abcdef4b775213c23a8bd74f5");
+	check_partial_oid(
+		big, GIT_OID_HEXSZ - 3, &in, "16a0123456789abcdef4b775213c23a8bd74f");
+}