context: don't count deleted files as candidates for path conflicts in IMM

This patch makes sure we don't consider the deleted files in our IMM wctx
as potential conflicts while calculating paths conflicts. This fixes the bug
demonstrated in previous patch.

Differential Revision: https://phab.mercurial-scm.org/D4543

mercurial/context.py

@@ -1910,14 +1910,19 b' class overlayworkingctx(committablectx):'
         # in p1 (test that p1 doesn't any paths matching `path/*`).
         match = matchmod.match('/', '', [path + '/'], default=b'relpath')
         matches = self.p1().manifest().matches(match)
-        if len(matches) > 0:
-            if len(matches) == 1 and matches.keys()[0] == path:
+        mfiles = matches.keys()
+        if len(mfiles) > 0:
+            if len(mfiles) == 1 and mfiles[0] == path:
+                return
+            # omit the files which are deleted in current IMM wctx
+            mfiles = [m for m in mfiles if self._cache[m]['exists']]
+            if not mfiles:
                 return
             raise error.Abort("error: file '%s' cannot be written because "
                               " '%s/' is a folder in %s (containing %d "
                               "entries: %s)"
-                              % (path, path, self.p1(), len(matches),
-                                 ', '.join(matches.keys())))
+                              % (path, path, self.p1(), len(mfiles),
+                                 ', '.join(mfiles)))
 
     def write(self, path, data, flags='', **kwargs):
         if data is None:

tests/test-rebase-inmemory.t

@@ -218,8 +218,25 b' Test reporting of path conflicts'
   
   $ hg rebase -r . -d 5
   rebasing 7:855e9797387e "added a back!" (tip)
-  abort: error: file 'a' cannot be written because  'a/' is a folder in 9b94b9373deb (containing 1 entries: a/a)
-  [255]
+  saved backup bundle to $TESTTMP/repo1/repo2/.hg/strip-backup/855e9797387e-81ee4c5d-rebase.hg
+
+  $ hg tglog
+  @  7: bb3f02be2688 'added a back!'
+  |
+  | o  6: d14530e5e3e6 'added bar'
+  | |
+  o |  5: 9b94b9373deb 'added foo'
+  |/
+  o  4: c6ad37a4f250 'a/a'
+  |
+  | o  3: 844a7de3e617 'c'
+  | |
+  o |  2: 09c044d2cb43 'd'
+  | |
+  o |  1: fc055c3b4d33 'b'
+  |/
+  o  0: b173517d0057 'a'
+  
 
   $ cd ..