subrepo: fix pruning of subrepo filenames in dirstate (issue2619)

mercurial/dirstate.py

@@ -506,7 +506,7 b' class dirstate(object):'
             if files[i] < subpath:
                 i += 1
                 continue
-            while files and files[i].startswith(subpath):
+            while i < len(files) and files[i].startswith(subpath):
                 del files[i]
             j += 1
 

tests/test-subrepo-recursion.t

@@ -346,3 +346,15 b' Test missing subrepo:'
   $ rm -r foo
   $ hg status -S
   warning: error "unknown revision '65903cebad86f1a84bd4f1134f62fa7dcb7a1c98'" in subrepository "foo"
+
+Issue2619: IndexError: list index out of range on hg add with subrepos
+The subrepo must sorts after the explicit filename.
+
+  $ cd ..
+  $ hg init test
+  $ cd test
+  $ hg init x
+  $ echo "x = x" >> .hgsub
+  $ hg add .hgsub
+  $ touch a x/a
+  $ hg add a x/a