tests/test-issue612.t

overlayworkingctx: fix exception in metadata-only inmemory merges (issue5960)

If there was a metadata-only mutation, such as +x or -x on a file, we would
create a cache entry with None for data, and this would cause problems later on
when some code tried to run fctx.data() or similar, and was expecting a string.

My original fix for this involved passing data=self._wrappedctx[path].data() in
setflags(), but this version seems slightly better - this way, if we ever call
write() and then call setflags(), we don't destroy the data that we wrote that's
in the cache. I haven't verified that other fields aren't destroyed, such as
date or flags :)

Differential Revision: https://phab.mercurial-scm.org/D4287

https://bz.mercurial-scm.org/612

  $ hg init
  $ mkdir src
  $ echo a > src/a.c
  $ hg ci -Ama
  adding src/a.c

  $ hg mv src source
  moving src/a.c to source/a.c

  $ hg ci -Ammove

  $ hg co -C 0
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ echo new > src/a.c
  $ echo compiled > src/a.o
  $ hg ci -mupdate
  created new head

  $ hg status
  ? src/a.o

  $ hg merge
  merging src/a.c and source/a.c to source/a.c
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg status
  M source/a.c
  R src/a.c
  ? src/a.o