credential-cache: respect authtype capability

Previously, credential-cache populated authtype regardless whether
"get" request had authtype capability. As documented in
git-credential.txt, authtype "should not be sent unless the appropriate
capability ... is provided".

Add test. Without this change, the test failed because "credential fill"
printed an incomplete credential with only protocol and host attributes
(the unexpected authtype attribute was discarded by credential.c).

Signed-off-by: M Hickford <mirth.hickford@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: hickford

Diff for: builtin/credential-cache--daemon.c

@@ -142,9 +142,9 @@ static void serve_one_client(FILE *in, FILE *out)
 				fprintf(out, "username=%s\n", e->item.username);
 			if (e->item.password)
 				fprintf(out, "password=%s\n", e->item.password);
-			if (credential_has_capability(&c.capa_authtype, CREDENTIAL_OP_HELPER) && e->item.authtype)
+			if (credential_has_capability(&c.capa_authtype, CREDENTIAL_OP_RESPONSE) && e->item.authtype)
 				fprintf(out, "authtype=%s\n", e->item.authtype);
-			if (credential_has_capability(&c.capa_authtype, CREDENTIAL_OP_HELPER) && e->item.credential)
+			if (credential_has_capability(&c.capa_authtype, CREDENTIAL_OP_RESPONSE) && e->item.credential)
 				fprintf(out, "credential=%s\n", e->item.credential);
 			if (e->item.password_expiry_utc != TIME_MAX)
 				fprintf(out, "password_expiry_utc=%"PRItime"\n",

Diff for: t/lib-credential.sh

@@ -566,6 +566,21 @@ helper_test_authtype() {
 		EOF
 	'
 
+	test_expect_success "helper ($HELPER) gets authtype and credential only if request has authtype capability" '
+		check fill $HELPER <<-\EOF
+		protocol=https
+		host=git.example.com
+		--
+		protocol=https
+		host=git.example.com
+		username=askpass-username
+		password=askpass-password
+		--
+		askpass: Username for '\''https://git.example.com'\'':
+		askpass: Password for '\''https://askpass-username@git.example.com'\'':
+		EOF
+	'
+
 	test_expect_success "helper ($HELPER) stores authtype and credential with username" '
 		check approve $HELPER <<-\EOF
 		capability[]=authtype