Merge branch 'ps/fetch-output-format'

Merge branch 'ps/fetch-output-format'

"git fetch" learned the "--porcelain" option that emits what it did
in a machine-parseable format.

* ps/fetch-output-format:
  fetch: introduce machine-parseable "porcelain" output format
  fetch: move option related variables into main function
  fetch: lift up parsing of "fetch.output" config variable
  fetch: introduce `display_format` enum
  fetch: refactor calculation of the display table width
  fetch: print left-hand side when fetching HEAD:foo
  fetch: add a test to exercise invalid output formats
  fetch: split out tests for output format
  fetch: fix `--no-recurse-submodules` with multi-remote fetches