git: avoid calling aliased builtins via their dashed form

git: avoid calling aliased builtins via their dashed form

This is one of the few places where Git violates its own deprecation of
the dashed form. It is not necessary, either.

As of 595d59e2b53 (git.c: ignore pager.* when launching builtin as
dashed external, 2017-08-02), Git wants to ignore the pager.* config
setting when expanding aliases. So let's strip out the
check_pager_config(<command-name>) call from the copy-edited code.

This code actually made it into upstream git.git already, but it was
disabled in `#if 0 ... #endif` guards so far.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>