tests/test-issue612.t

templater: allow piping generator-type function output to filters

Template functions use "yield"s assuming that the result will be combined
into a string, which means both "f -> str" and "f -> generator" should behave
in the same way.

Before this patch, piping generator function resulted in a cryptic error.
We had to insert "|stringify" in this case.

  $ hg log --template '{if(author, author)|user}\n'
  abort: template filter 'userfilter' is not compatible with keyword
  '[(<function runsymbol at 0x7f5af2e8d8c0>, 'author'),
    (<function runsymbol at 0x7f5af2e8d8c0>, 'author')]'

http://mercurial.selenic.com/bts/issue612

  $ 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 (glob)

  $ 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