Merge branch 'js/log-to-diffopt-file'

Merge branch 'js/log-to-diffopt-file'

The commands in the "log/diff" family have had an FILE* pointer in the
data structure they pass around for a long time, but some codepaths
used to always write to the standard output.  As a preparatory step
to make "git format-patch" available to the internal callers, these
codepaths have been updated to consistently write into that FILE*
instead.

* js/log-to-diffopt-file:
  mingw: fix the shortlog --output=<file> test
  diff: do not color output when --color=auto and --output=<file> is given
  t4211: ensure that log respects --output=<file>
  shortlog: respect the --output=<file> setting
  format-patch: use stdout directly
  format-patch: avoid freopen()
  format-patch: explicitly switch off color when writing to files
  shortlog: support outputting to streams other than stdout
  graph: respect the diffopt.file setting
  line-log: respect diffopt's configured output file stream
  log-tree: respect diffopt's configured output file stream
  log: prepare log/log-tree to reuse the diffopt.close_file attribute