subrepo: don't abort in add when non-hg subrepos are present (issue4513)

This change should have been part of 9994f45ba714.

mercurial/subrepo.py

@@ -435,7 +435,7 b' class abstractsubrepo(object):'
         """
         raise NotImplementedError
 
-    def add(self, ui, match, dryrun, listsubrepos, prefix, explicitonly):
+    def add(self, ui, match, prefix, explicitonly, **opts):
         return []
 
     def addremove(self, matcher, prefix, opts, dry_run, similarity):

tests/test-subrepo-git.t

@@ -133,6 +133,7 b' clone root separately, make different lo'
   $ echo f > f
   $ hg status --subrepos
   ? s/f
+  $ hg add .
   $ git add f
   $ cd ..
 

tests/test-subrepo-svn.t

@@ -439,8 +439,9 b' are unknown directories being replaced b'
   $ hg add .hgsub
   $ hg ci -m addsub
   $ echo a > a
-  $ hg ci -Am adda
+  $ hg add .
   adding a
+  $ hg ci -m adda
   $ hg up 0
   0 files updated, 0 files merged, 1 files removed, 0 files unresolved
   $ svn up -qr6 s