Both 'pickaxe' (searching changes) and 'grep' (searching files)
require basic 'search' feature to be enabled to work.  Enabling
e.g. only 'pickaxe' won't work.

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Signed-off-by: NJakub Narebski <jnareb@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>