test: demonstrate crash with in-memory rebase and copies

In the added test case, there is a merge commit that has one obsolete
parent with a rename. Since the rename is not in the other parent,
pathcopies() from that other parent will include the copy. Then when
we try to rebase this merge commit onto another commit that has the
same content changes, but no tracking of the rename (because it was
done with "hg remove; hg add" instead of "hg mv"), we try to propagate
the copy information. That fails because overlayworkingctx expects a
file to be modified if it's going to have copy information.

Differential Revision: https://phab.mercurial-scm.org/D6132

tests/test-rebase-inmemory.t

@@ -718,3 +718,43 b' issue5960: this was raising an Attribute'
   diff --git a/foo.txt b/foo.txt
   old mode 100644
   new mode 100755
+
+Test rebasing a commit with copy information, but no content changes
+
+  $ cd ..
+  $ hg clone -q repo1 merge-and-rename
+  $ cd merge-and-rename
+  $ cat << EOF >> .hg/hgrc
+  > [experimental]
+  > evolution.createmarkers=True
+  > evolution.allowunstable=True
+  > EOF
+  $ hg co -q 1
+  $ hg mv d e
+  $ hg ci -qm 'rename d to e'
+  $ hg co -q 3
+  $ hg merge -q 4
+  $ hg ci -m 'merge'
+  $ hg co -q 2
+  $ mv d e
+  $ hg addremove -qs 0
+  $ hg ci -qm 'untracked rename of d to e'
+  $ hg debugobsolete -q `hg log -T '{node}' -r 4` `hg log -T '{node}' -r .`
+  1 new orphan changesets
+  $ hg tglog
+  @  6: 676538af172d 'untracked rename of d to e'
+  |
+  | *    5: 71cb43376053 'merge'
+  | |\
+  | | x  4: 2c8b5dad7956 'rename d to e'
+  | | |
+  | o |  3: ca58782ad1e4 'b'
+  |/ /
+  o /  2: 814f6bd05178 'c'
+  |/
+  o  1: 02952614a83d 'd'
+  |
+  o  0: b173517d0057 'a'
+  
+  $ hg rebase -b 5 -d tip 2>&1 | grep '** ProgrammingError'
+  ** ProgrammingError: markcopied() called on clean context