Merge branch 'sk/spawn-less-case-insensitively-from-grep-O-i' into maint

"git grep -O" to show the lines that hit in the pager did not work
well with case insensitive search.  We now spawn "less" with its
"-I" option when it is used as the pager (which is the default).

* sk/spawn-less-case-insensitively-from-grep-O-i:
  git grep -O -i: if the pager is 'less', pass the '-I' option

diff --cc builtin/grep.c
Simple merge