tests: demonstrate that IMM needs to be smarter with path conflicts

When we try to rebase a commit which deletes an existing file and make a
directory of the same name, rebase with IMM aborts. It should work fine just
like the without IMM case.

Differential Revision: https://phab.mercurial-scm.org/D4299

tests/test-rebase-inmemory.t

@@ -156,6 +156,30 b' Rebase the working copy parent'
   |/
   o  0: b173517d0057 'a'
 
+
+Test reporting of path conflicts
+
+  $ hg rm a
+  $ mkdir a
+  $ touch a/a
+  $ hg ci -Am "a/a"
+  adding a/a
+  $ hg tglog
+  @  4: daf7dfc139cb 'a/a'
+  |
+  o  3: 844a7de3e617 'c'
+  |
+  | o  2: 09c044d2cb43 'd'
+  | |
+  | o  1: fc055c3b4d33 'b'
+  |/
+  o  0: b173517d0057 'a'
+  
+  $ hg rebase -r . -d 2
+  rebasing 4:daf7dfc139cb "a/a" (tip)
+  abort: error: 'a/a' conflicts with file 'a' in 2.
+  [255]
+
   $ cd ..
 
 Test dry-run rebasing