merge: make merge.renormalize work for all uses of merge machinery
The 'merge' command is not the only one that does merges; other commands
like checkout -m or rebase do as well. Unfortunately, the only area of
the code that checked for the "merge.renormalize" config setting was in
builtin/merge.c, meaning it could only affect merges performed by the
"merge" command. Move the handling of this config setting to
merge_recursive_config() so that other commands can benefit from it as
well. Fixes a few tests in t6038.
Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>