core: support %j in unit dependency resolution

Commit 250e9fadbcc0ca90e697d7efb40855b054ed3b8f introduced
support for %j/%J specifier in unit files.  The function
unit_name_printf is used in unit dependency resolution,
such as Wants / After directives, but was missing support
for the %j.  Add to allow directives such as:

    [Unit]
    Wants=bar-%j.target

Fixes: systemd/systemd#11217
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>

src/core/unit-printf.c

@@ -195,6 +195,7 @@ int unit_name_printf(Unit *u, const char* format, char **ret) {
                 { 'N', specifier_prefix_and_instance, NULL },
                 { 'p', specifier_prefix,              NULL },
                 { 'i', specifier_string,              u->instance },
+                { 'j', specifier_last_component,      NULL },
 
                 { 'g', specifier_group_name,          NULL },
                 { 'G', specifier_group_id,            NULL },

test/TEST-28-PERCENTJ-WANTEDBY/Makefile

@@ -0,0 +1,9 @@
+BUILD_DIR=$(shell ../../tools/find-build-dir.sh)
+
+all setup run:
+	@basedir=../.. TEST_BASE_DIR=../ BUILD_DIR=$(BUILD_DIR) ./test.sh --$@
+
+clean clean-again:
+	@basedir=../.. TEST_BASE_DIR=../ BUILD_DIR=$(BUILD_DIR) ./test.sh --clean
+
+.PHONY: all setup run clean clean-again

test/TEST-28-PERCENTJ-WANTEDBY/test.sh

@@ -0,0 +1,68 @@
+#!/bin/bash
+# -*- mode: shell-script; indent-tabs-mode: nil; sh-basic-offset: 4; -*-
+# ex: ts=8 sw=4 sts=4 et filetype=sh
+set -e
+TEST_DESCRIPTION="Ensure %j Wants directives work"
+RUN_IN_UNPRIVILEGED_CONTAINER=yes
+
+. $TEST_BASE_DIR/test-functions
+
+test_setup() {
+    create_empty_image
+    mkdir -p $TESTDIR/root
+    mount ${LOOPDEV}p1 $TESTDIR/root
+
+    # Create what will eventually be our root filesystem onto an overlay
+    (
+        LOG_LEVEL=5
+        eval $(udevadm info --export --query=env --name=${LOOPDEV}p2)
+
+        setup_basic_environment
+
+        # Set up the services.
+        cat >$initdir/etc/systemd/system/specifier-j-wants.service << EOF
+[Unit]
+Description=Wants with percent-j specifier
+Wants=specifier-j-depends-%j.service
+After=specifier-j-depends-%j.service
+
+[Service]
+Type=oneshot
+ExecStart=test -f /tmp/test-specifier-j-%j
+ExecStart=/bin/sh -c 'echo OK > /testok'
+EOF
+        cat >$initdir/etc/systemd/system/specifier-j-depends-wants.service << EOF
+[Unit]
+Description=Dependent service for percent-j specifier
+
+[Service]
+Type=oneshot
+ExecStart=touch /tmp/test-specifier-j-wants
+EOF
+        cat >$initdir/etc/systemd/system/testsuite.service << EOF
+[Unit]
+Description=Testsuite: Ensure %j Wants directives work
+Wants=specifier-j-wants.service
+After=specifier-j-wants.service
+
+[Service]
+Type=oneshot
+ExecStart=/bin/true
+EOF
+
+        setup_testsuite
+    ) || return 1
+    setup_nspawn_root
+
+        # mask some services that we do not want to run in these tests
+        ln -s /dev/null $initdir/etc/systemd/system/systemd-hwdb-update.service
+        ln -s /dev/null $initdir/etc/systemd/system/systemd-journal-catalog-update.service
+        ln -s /dev/null $initdir/etc/systemd/system/systemd-networkd.service
+        ln -s /dev/null $initdir/etc/systemd/system/systemd-networkd.socket
+        ln -s /dev/null $initdir/etc/systemd/system/systemd-resolved.service
+
+    ddebug "umount $TESTDIR/root"
+    umount $TESTDIR/root
+}
+
+do_test "$@"