Merge branch 'jc/sane-grep'

Merge branch 'jc/sane-grep'

Recent versions of GNU grep is pickier than before to decide if a
file is "binary" and refuse to give line-oriented hits when we
expect it to, unless explicitly told with "-a" option.  As our
scripted Porcelains use sane_grep wrapper for line-oriented data,
even when the line may contain non-ASCII payload we took from
end-user data, use "grep -a" to implement sane_grep wrapper when
using an implementation of "grep" that takes the "-a" option.

* jc/sane-grep:
  rebase-i: clarify "is this commit relevant?" test
  sane_grep: pass "-a" if grep accepts it