tests/test-issue842.t

make_file: always return a fresh file handle that can be closed

Currently, cmdutil.make_file() will return a freshly made file handle,
except when given a pattern of '-'. If callers would want to close the
handle, they would have to make sure that it's neither sys.stdin or
sys.stdout. Instead, returning a duplicate of either of the two
ensures that make_file() lives up to its name and creates a new
file handle regardless of the input.

http://mercurial.selenic.com/bts/issue842

  $ hg init
  $ echo foo > a
  $ hg ci -Ama
  adding a

  $ hg up -r0000
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ echo bar > a

Should issue new head warning:

  $ hg ci -Amb
  adding a
  created new head

  $ hg up -r0000
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ echo stuffy > a

Should not issue new head warning:

  $ hg ci -q -Amc

  $ hg up -r0000
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ echo crap > a
  $ hg branch testing
  marked working directory as branch testing

Should not issue warning:

  $ hg ci -q -Amd