[PATCH v2 09/12] pretty: add %C(auto) for auto-coloring on the next placeholder

@@ -154,7 +154,8 @@ The placeholders are:
   adding `auto,` at the beginning will emit color only when colors are
   enabled for log output (by `color.diff`, `color.ui`, or `--color`, and
   respecting the `auto` settings of the former if we are going to a
-  terminal)
+  terminal). `auto` alone (i.e. `%C(auto)`) will turn on auto coloring
+  on the following placeholder.
 - '%m': left, right or boundary mark
 - '%n': newline
 - '%%': a raw '%'

@@ -774,6 +774,7 @@ struct format_commit_context {
 	char *message;
 	char *commit_encoding;
 	size_t width, indent1, indent2;
+	int auto_color;
 
 	/* These offsets are relative to the start of the commit message. */
 	struct chunk author;

@@ -1011,7 +1012,7 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 	const struct commit *commit = c->commit;
 	const char *msg = c->message;
 	struct commit_list *p;
-	int h1, h2;
+	int h1, h2, use_color;
 
 	/* these are independent of the commit */
 	switch (placeholder[0]) {

@@ -1023,6 +1024,10 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 
 			if (!end)
 				return 0;
+			if (!prefixcmp(begin, "auto)")) {
+				c->auto_color = 1;
+				return end - placeholder + 1;
+			}
 			if (!prefixcmp(begin, "auto,")) {
 				if (!want_color(c->pretty_ctx->color))
 					return end - placeholder + 1;

@@ -1090,16 +1095,22 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 	/* these depend on the commit */
 	if (!commit->object.parsed)
 		parse_object(commit->object.sha1);
+	use_color = c->auto_color;
+	c->auto_color = 0;
 
 	switch (placeholder[0]) {
 	case 'H':		/* commit hash */
+		strbuf_addstr(sb, diff_get_color(use_color, DIFF_COMMIT));
 		strbuf_addstr(sb, sha1_to_hex(commit->object.sha1));
+		strbuf_addstr(sb, diff_get_color(use_color, DIFF_RESET));
 		return 1;
 	case 'h':		/* abbreviated commit hash */
+		strbuf_addstr(sb, diff_get_color(use_color, DIFF_COMMIT));
 		if (add_again(sb, &c->abbrev_commit_hash))
 			return 1;
 		strbuf_addstr(sb, find_unique_abbrev(commit->object.sha1,
 						     c->pretty_ctx->abbrev));
+		strbuf_addstr(sb, diff_get_color(use_color, DIFF_RESET));
 		c->abbrev_commit_hash.len = sb->len - c->abbrev_commit_hash.off;
 		return 1;
 	case 'T':		/* tree hash */

@@ -1136,7 +1147,7 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 		strbuf_addstr(sb, get_revision_mark(NULL, commit));
 		return 1;
 	case 'd':
-		format_decoration(sb, commit, 0);
+		format_decoration(sb, commit, use_color);
 		return 1;
 	case 'g':		/* reflog info */
 		switch(placeholder[1]) {