Merge branch 'lo/repo-info' into next

A new subcommand "git repo" gives users a way to grab various
repository characteristics.

* lo/repo-info:
  repo: add the --format flag
  repo: add the field layout.shallow
  repo: add the field layout.bare
  repo: add the field references.format
  repo: declare the repo command

diff --cc Documentation/meson.build
Simple merge

diff --cc Makefile
Simple merge

diff --cc git.c
Simple merge

diff --cc meson.build
Simple merge

diff --cc t/meson.build
Simple merge