Merge branch 'jk/color-and-pager'

* jk/color-and-pager:
  want_color: automatically fallback to color.ui
  diff: don't load color config in plumbing
  config: refactor get_colorbool function
  color: delay auto-color decision until point of use
  git_config_colorbool: refactor stdout_is_tty handling
  diff: refactor COLOR_DIFF from a flag into an int
  setup_pager: set GIT_PAGER_IN_USE
  t7006: use test_config helpers
  test-lib: add helper functions for config
  t7006: modernize calls to unset

Conflicts:
	builtin/commit.c
	parse-options.c
diff --git a/parse-options-cb.c b/parse-options-cb.c
index c248f66..6db0921 100644
--- a/parse-options-cb.c
+++ b/parse-options-cb.c
@@ -40,7 +40,7 @@
 
 	if (!arg)
 		arg = unset ? "never" : (const char *)opt->defval;
-	value = git_config_colorbool(NULL, arg, -1);
+	value = git_config_colorbool(NULL, arg);
 	if (value < 0)
 		return opterror(opt,
 			"expects \"always\", \"auto\", or \"never\"", 0);