Merge branch 'ma/config-page-only-in-list-mode'

Merge branch 'ma/config-page-only-in-list-mode'

In a way similar to how "git tag" learned to honor the pager
setting only in the list mode, "git config" learned to ignore the
pager setting when it is used for setting values (i.e. when the
purpose of the operation is not to "show").

* ma/config-page-only-in-list-mode:
  config: change default of `pager.config` to "on"
  config: respect `pager.config` in list/get-mode only
  t7006: add tests for how git config paginates