pretty: support %>> that steal trailing spaces

This is pretty useful in `%<(100)%s%Cred%>(20)% an' where %s does not
use up all 100 columns and %an needs more than 20 columns. By
replacing %>(20) with %>>(20), %an can steal spaces from %s.

%>> understands escape sequences, so %Cred does not stop it from
stealing spaces in %<(100).

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/pretty.c b/pretty.c
index f7c6442e71..d59579a2c0 100644
--- a/pretty.c
+++ b/pretty.c
@@ -773,6 +773,7 @@ enum flush_type {
 	no_flush,
 	flush_right,
 	flush_left,
+	flush_left_and_steal,
 	flush_both
 };
 
@@ -1026,6 +1027,9 @@ static size_t parse_padding_placeholder(struct strbuf *sb,
 		if (*ch == '<') {
 			flush_type = flush_both;
 			ch++;
+		} else if (*ch == '>') {
+			flush_type = flush_left_and_steal;
+			ch++;
 		} else
 			flush_type = flush_left;
 		break;
@@ -1334,6 +1338,36 @@ static size_t format_and_pad_commit(struct strbuf *sb, /* in UTF-8 */
 		total_consumed++;
 	}
 	len = utf8_strnwidth(local_sb.buf, -1, 1);
+
+	if (c->flush_type == flush_left_and_steal) {
+		const char *ch = sb->buf + sb->len - 1;
+		while (len > padding && ch > sb->buf) {
+			const char *p;
+			if (*ch == ' ') {
+				ch--;
+				padding++;
+				continue;
+			}
+			/* check for trailing ansi sequences */
+			if (*ch != 'm')
+				break;
+			p = ch - 1;
+			while (ch - p < 10 && *p != '\033')
+				p--;
+			if (*p != '\033' ||
+			    ch + 1 - p != display_mode_esc_sequence_len(p))
+				break;
+			/*
+			 * got a good ansi sequence, put it back to
+			 * local_sb as we're cutting sb
+			 */
+			strbuf_insert(&local_sb, 0, p, ch + 1 - p);
+			ch = p - 1;
+		}
+		strbuf_setlen(sb, ch + 1 - sb->buf);
+		c->flush_type = flush_left;
+	}
+
 	if (len > padding) {
 		switch (c->truncate) {
 		case trunc_left: