diff --git a/mercurial/subrepo.py b/mercurial/subrepo.py
--- a/mercurial/subrepo.py
+++ b/mercurial/subrepo.py
@@ -1526,14 +1526,15 @@ class gitsubrepo(abstractsubrepo):
     def add(self, ui, match, prefix, explicitonly, **opts):
         if self._gitmissing():
             return []
-        if match.files():
-            files = match.files()
-        else:
-            (modified, added, removed,
-             deleted, unknown, ignored, clean) = self.status(None)
-            files = unknown
+
+        (modified, added, removed,
+         deleted, unknown, ignored, clean) = self.status(None)
 
-        files = [f for f in files if match(f)]
+        # Unknown files not of interest will be rejected by the matcher
+        files = unknown
+        files.extend(match.files())
+
+        files = [f for f in sorted(set(files)) if match(f)]
         for f in files:
             exact = match.exact(f)
             command = ["add"]
diff --git a/tests/test-subrepo-git.t b/tests/test-subrepo-git.t
--- a/tests/test-subrepo-git.t
+++ b/tests/test-subrepo-git.t
@@ -922,11 +922,11 @@ make sure everything is reverted correct
   > *.python
   > EOF
   $ hg add .hgignore
-  $ hg add --subrepos "glob:**.python"
+  $ hg add --subrepos "glob:**.python" s/barfoo
   adding s/snake.python (glob)
   $ hg st --subrepos s
+  A s/barfoo
   A s/snake.python
-  ? s/barfoo
   ? s/c.c
   ? s/cpp.cpp
   ? s/foobar.orig