fs-util,label: introduce symlink_atomic_full() and symlink_atomic_full_label()

These new functions optionally create symlink of relative path.

src/basic/fs-util.c

@@ -432,13 +432,21 @@ int symlink_idempotent(const char *from, const char *to, bool make_relative) {
         return 0;
 }
 
-int symlink_atomic(const char *from, const char *to) {
-        _cleanup_free_ char *t = NULL;
+int symlink_atomic_full(const char *from, const char *to, bool make_relative) {
+        _cleanup_free_ char *relpath = NULL, *t = NULL;
         int r;
 
         assert(from);
         assert(to);
 
+        if (make_relative) {
+                r = path_make_relative_parent(to, from, &relpath);
+                if (r < 0)
+                        return r;
+
+                from = relpath;
+        }
+
         r = tempfn_random(to, NULL, &t);
         if (r < 0)
                 return r;

src/basic/fs-util.h

@@ -58,7 +58,10 @@ static inline int touch(const char *path) {
 
 int symlink_idempotent(const char *from, const char *to, bool make_relative);
 
-int symlink_atomic(const char *from, const char *to);
+int symlink_atomic_full(const char *from, const char *to, bool make_relative);
+static inline int symlink_atomic(const char *from, const char *to) {
+        return symlink_atomic_full(from, to, false);
+}
 int mknod_atomic(const char *path, mode_t mode, dev_t dev);
 int mkfifo_atomic(const char *path, mode_t mode);
 int mkfifoat_atomic(int dir_fd, const char *path, mode_t mode);