Merge branch 'jk/color-variable-fixes'

Some places in the code confused a variable that is *not* a boolean
to enable color but is an enum that records what the user requested
to do about color.  A couple of bugs of this sort have been fixed,
while the code has been cleaned up to prevent similar bugs in the
future.

* jk/color-variable-fixes:
  config: store want_color() result in a separate bool
  add-interactive: retain colorbool values longer
  color: return bool from want_color()
  color: use git_colorbool enum type to store colorbools
  pretty: use format_commit_context.auto_color as colorbool
  diff: stop passing ecbdata->use_color as boolean
  diff: pass o->use_color directly to fill_metainfo()
  diff: don't use diff_options.use_color as a strict bool
  diff: simplify color_moved check when flushing
  grep: don't treat grep_opt.color as a strict bool
  color: return enum from git_config_colorbool()
  color: use GIT_COLOR_* instead of numeric constants

diff.h

@@ -7,6 +7,7 @@
 #include "hash.h"
 #include "pathspec.h"
 #include "strbuf.h"
+#include "color.h"
 
 struct oidset;
 
@@ -283,7 +284,7 @@ struct diff_options {
 	/* diff-filter bits */
 	unsigned int filter, filter_not;
 
-	int use_color;
+	enum git_colorbool use_color;
 
 	/* Number of context lines to generate in patch output. */
 	int context;
@@ -469,7 +470,7 @@ enum color_diff {
 	DIFF_FILE_NEW_BOLD = 22,
 };
 
-const char *diff_get_color(int diff_use_color, enum color_diff ix);
+const char *diff_get_color(enum git_colorbool diff_use_color, enum color_diff ix);
 #define diff_get_color_opt(o, ix) \
 	diff_get_color((o)->use_color, ix)