process_pipe: allow creating item w/o user/group/uid/gid, see #7249

src/borg/archive.py

@@ -1399,28 +1399,32 @@ class FilesystemObjectProcessors:
             item.update(self.metadata_collector.stat_attrs(st, path))  # can't use FD here?
             return status
 
-    def process_pipe(self, *, path, cache, fd, mode, user, group):
+    def process_pipe(self, *, path, cache, fd, mode, user=None, group=None):
         status = "i"  # stdin (or other pipe)
         self.print_file_status(status, path)
         status = None  # we already printed the status
+        if user is not None:
             uid = user2uid(user)
             if uid is None:
                 raise Error("no such user: %s" % user)
+        else:
+            uid = None
+        if group is not None:
             gid = group2gid(group)
             if gid is None:
                 raise Error("no such group: %s" % group)
+        else:
+            gid = None
         t = int(time.time()) * 1000000000
-        item = Item(
-            path=path,
-            mode=mode & 0o107777 | 0o100000,  # forcing regular file mode
-            uid=uid,
-            user=user,
-            gid=gid,
-            group=group,
-            mtime=t,
-            atime=t,
-            ctime=t,
-        )
+        item = Item(path=path, mode=mode & 0o107777 | 0o100000, mtime=t, atime=t, ctime=t)  # forcing regular file mode
+        if user is not None:
+            item.user = user
+        if group is not None:
+            item.group = group
+        if uid is not None:
+            item.uid = uid
+        if gid is not None:
+            item.gid = gid
         self.process_file_chunks(item, cache, self.stats, self.show_progress, backup_io_iter(self.chunker.chunkify(fd)))
         item.get_size(memorize=True)
         self.stats.nfiles += 1