subrepo: be more careful with deletions of .hgsub and .hgsubstate (issue2844)

We shouldn't try to process subrepos if .hgsub isn't present and we
should remove .hgsubstate if .hgsub is marked for removal.

mercurial/localrepo.py

@@ -944,6 +944,8 b' class localrepository(repo.repository):'
             # check subrepos
             subs = []
             removedsubs = set()
+            if '.hgsub' in wctx:
+                # only manage subrepos and .hgsubstate if .hgsub is present
             for p in wctx.parents():
                 removedsubs.update(s for s in p.substate if match(s))
             for s in wctx.substate:
@@ -953,9 +955,17 b' class localrepository(repo.repository):'
             if (subs or removedsubs):
                 if (not match('.hgsub') and
                     '.hgsub' in (wctx.modified() + wctx.added())):
-                    raise util.Abort(_("can't commit subrepos without .hgsub"))
+                        raise util.Abort(
+                            _("can't commit subrepos without .hgsub"))
                 if '.hgsubstate' not in changes[0]:
                     changes[0].insert(0, '.hgsubstate')
+                        if '.hgsubstate' in changes[2]:
+                            changes[2].remove('.hgsubstate')
+            elif '.hgsub' in changes[2]:
+                # clean up .hgsubstate when .hgsub is removed
+                if ('.hgsubstate' in wctx and
+                    '.hgsubstate' not in changes[0] + changes[1] + changes[2]):
+                    changes[2].insert(0, '.hgsubstate')
 
             if subs and not self.ui.configbool('ui', 'commitsubrepos', True):
                 changedsubs = [s for s in subs if wctx.sub(s).dirty(True)]

tests/test-subrepo.t

@@ -500,6 +500,7 b' test subrepo delete from .hgsubstate'
   $ hg -R testdelete remove testdelete/.hgsub
   $ hg -R testdelete ci -m ".hgsub deleted"
   $ cat testdelete/.hgsubstate
+  bdf5c9a3103743d900b12ae0db3ffdcfd7b0d878 nested
 
 test repository cloning
 
@@ -823,3 +824,36 b' Test subrepo already at intended revisio'
   fc627a69481f
   $ hg -R t id 
   e95bcfa18a35
+
+Test that removing .hgsubstate doesn't break anything:
+
+  $ hg rm -f .hgsubstate
+  $ hg ci -mrm
+  committing subrepository s
+  committing subrepository t
+  created new head
+  $ hg log -vr tip
+  changeset:   14:3941e0aa5236
+  tag:         tip
+  parent:      11:365661e5936a
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  description:
+  rm
+  
+  
+
+Test that removing .hgsub removes .hgsubstate:
+
+  $ hg rm .hgsub
+  $ hg ci -mrm2
+  $ hg log -vr tip
+  changeset:   15:8b31de9d13d1
+  tag:         tip
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  files:       .hgsub .hgsubstate
+  description:
+  rm2
+  
+