Currently when git grep is used outside of a git repository without the
--no-index option git simply dies. For convenience, add a
grep.fallbackToNoIndex configuration variable. If set to true, git grep
behaves like git grep --no-index if it is run outside of a git
repository. It defaults to false, preserving the current behavior.
Helped-by: Jeff King <peff@peff.net> Helped-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>