wt-status: use settings from git_diff_ui_config

wt-status: use settings from git_diff_ui_config

If you do something like

    - git add .
    - git status
    - git commit
    - git show (or git diff HEAD)

one would expect to have analogous output from git status and git show
(or similar diff-related programs). This is generally not the case, as
git status has hard coded values for diff related options.

With this commit the hard coded settings are dropped from the status
command in favour for values provided by git_diff_ui_config.

What follows are some remarks on the concrete options which were hard
coded in git status:

diffopt.detect_rename

Since the very beginning of git status in a3e870f2e2 ("Add "commit"
helper script", 2005-05-30), git status always used rename detection,
whereas with commands like show and log one had to activate it with a
command line option. After 5404c116aa ("diff: activate diff.renames by
default", 2016-02-25) the default behaves the same by coincidence, but
changing diff.renames to other values can break the consistency between
git status and other commands again. With this commit one control the
same default behaviour with diff.renames.

diffopt.rename_limit

Similarly one has the option diff.renamelimit to adjust this limit for
all commands but git status. With this commit git status will also honor
those.

diffopt.break_opt

Unlike the other two options this cannot be configured by a
configuration option yet. This commit will also change the default
behaviour to not use break rewrites. But as rename detection is most
likely on, this is dangerous to be activated anyway as one can see
here:

    https://public-inbox.org/git/xmqqegqaahnh.fsf@gitster.dls.corp.google.com/

Signed-off-by: Eckhard S. Maaß <eckhard.s.maass@gmail.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>