systemctl: fix silent failure when --root is not found

Some calls to lookup_path_init() were not followed by any log emission.
E.g.:
$ SYSTEMD_LOG_LEVEL=debug systemctl --root=/missing enable unit; echo $?
1

Let's add a helper function and use it in various places.

$ SYSTEMD_LOG_LEVEL=debug build/systemctl --root=/missing enable unit; echo $?
Failed to initialize unit search paths for root directory /missing: No such file or directory
1
$ SYSTEMCTL_SKIP_SYSV=1 build/systemctl --root=/missing enable unit; echo $?
Failed to initialize unit search paths for root directory /missing: No such file or directory
Failed to enable: No such file or directory.
1

The repeated error in the second case is not very nice, but this is a niche
case and I don't think it's worth the trouble to trying to avoid it.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/basic/path-lookup.h b/src/basic/path-lookup.h
index af85dc7b4f..1f0e5ea271 100644
--- a/src/basic/path-lookup.h
+++ b/src/basic/path-lookup.h
@@ -54,7 +54,8 @@ struct LookupPaths {
         char *temporary_dir;
 };
 
-int lookup_paths_init(LookupPaths *p, UnitFileScope scope, LookupPathsFlags flags, const char *root_dir);
+int lookup_paths_init(LookupPaths *lp, UnitFileScope scope, LookupPathsFlags flags, const char *root_dir);
+int lookup_paths_init_or_warn(LookupPaths *lp, UnitFileScope scope, LookupPathsFlags flags, const char *root_dir);
 
 int xdg_user_dirs(char ***ret_config_dirs, char ***ret_data_dirs);
 int xdg_user_runtime_dir(char **ret, const char *suffix);