Git 2.2.0-rc1

Signed-off-by: Junio C Hamano <gitster@pobox.com>
replace: Add some clarification to doc
replace: Add example to doc.
replace: clarify use with files or trees.
help: when passed an alias, display help for the aliased command.

if aliased command is a shell command, just name it (and identify it as
a shell command.

if aliased command has flags, display help for base command.
no gettext