diff: prepare for additional submodule formats

A future patch will add a new format for displaying the difference of
a submodule. Make it easier by changing how we store the current
selected format. Replace the DIFF_OPT flag with an enumeration, as each
format will be mutually exclusive.
Signed-off-by: NJacob Keller <jacob.keller@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

diff.c

@@ -132,9 +132,9 @@ static int parse_dirstat_params(struct diff_options *options, const char *params
 static int parse_submodule_params(struct diff_options *options, const char *value)
 {
 	if (!strcmp(value, "log"))
-		DIFF_OPT_SET(options, SUBMODULE_LOG);
+		options->submodule_format = DIFF_SUBMODULE_LOG;
 	else if (!strcmp(value, "short"))
-		DIFF_OPT_CLR(options, SUBMODULE_LOG);
+		options->submodule_format = DIFF_SUBMODULE_SHORT;
 	else
 		return -1;
 	return 0;
@@ -2300,9 +2300,9 @@ static void builtin_diff(const char *name_a,
 	struct strbuf header = STRBUF_INIT;
 	const char *line_prefix = diff_line_prefix(o);
 
-	if (DIFF_OPT_TST(o, SUBMODULE_LOG) &&
-			(!one->mode || S_ISGITLINK(one->mode)) &&
-			(!two->mode || S_ISGITLINK(two->mode))) {
+	if (o->submodule_format == DIFF_SUBMODULE_LOG &&
+	    (!one->mode || S_ISGITLINK(one->mode)) &&
+	    (!two->mode || S_ISGITLINK(two->mode))) {
 		const char *del = diff_get_color_opt(o, DIFF_FILE_OLD);
 		const char *add = diff_get_color_opt(o, DIFF_FILE_NEW);
 		show_submodule_summary(o->file, one->path ? one->path : two->path,
@@ -3916,7 +3916,7 @@ int diff_opt_parse(struct diff_options *options,
 		DIFF_OPT_SET(options, OVERRIDE_SUBMODULE_CONFIG);
 		handle_ignore_submodules_arg(options, arg);
 	} else if (!strcmp(arg, "--submodule"))
-		DIFF_OPT_SET(options, SUBMODULE_LOG);
+		options->submodule_format = DIFF_SUBMODULE_LOG;
 	else if (skip_prefix(arg, "--submodule=", &arg))
 		return parse_submodule_opt(options, arg);
 	else if (skip_prefix(arg, "--ws-error-highlight=", &arg))

diff.h

@@ -83,7 +83,6 @@ typedef struct strbuf *(*diff_prefix_fn_t)(struct diff_options *opt, void *data)
 #define DIFF_OPT_DIRSTAT_BY_FILE     (1 << 20)
 #define DIFF_OPT_ALLOW_TEXTCONV      (1 << 21)
 #define DIFF_OPT_DIFF_FROM_CONTENTS  (1 << 22)
-#define DIFF_OPT_SUBMODULE_LOG       (1 << 23)
 #define DIFF_OPT_DIRTY_SUBMODULES    (1 << 24)
 #define DIFF_OPT_IGNORE_UNTRACKED_IN_SUBMODULES (1 << 25)
 #define DIFF_OPT_IGNORE_DIRTY_SUBMODULES (1 << 26)
@@ -110,6 +109,11 @@ enum diff_words_type {
 	DIFF_WORDS_COLOR
 };
 
+enum diff_submodule_format {
+	DIFF_SUBMODULE_SHORT = 0,
+	DIFF_SUBMODULE_LOG
+};
+
 struct diff_options {
 	const char *orderfile;
 	const char *pickaxe;
@@ -157,6 +161,7 @@ struct diff_options {
 	int stat_count;
 	const char *word_regex;
 	enum diff_words_type word_diff;
+	enum diff_submodule_format submodule_format;
 
 	/* this is set by diffcore for DIFF_FORMAT_PATCH */
 	int found_changes;