Merge branch 'ma/grep-init-default'

Code clean-up.

* ma/grep-init-default:
  MyFirstObjectWalk: drop `init_walken_defaults()`
  grep: copy struct in one fell swoop
  grep: use designated initializers for `grep_defaults`
  grep: don't set up a "default" repo for grep

diff --cc builtin/log.c
Simple merge

diff --cc revision.c
Simple merge