Get rid of the duplicated getenv('GIT_MERGE_VERBOSITY') calls with the same
constant string argument. This makes code more readable and prevents typo in
the further development.
Signed-off-by: Andrey Okoshkin <a.okoshkin@samsung.com> Reviewed-by: Stefan Beller <sbeller@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>