built-in add -p: implement the 'g' ("goto") command

With this patch, it is now possible to see a summary of the available
hunks and to navigate between them (by number).

A test is added to verify that this behavior matches the one of the Perl
version of `git add -p`.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

add-patch.c

@@ -955,6 +955,54 @@ static int edit_hunk_loop(struct add_p_state *s,
 	}
 }
 
+#define SUMMARY_HEADER_WIDTH 20
+#define SUMMARY_LINE_WIDTH 80
+static void summarize_hunk(struct add_p_state *s, struct hunk *hunk,
+			   struct strbuf *out)
+{
+	struct hunk_header *header = &hunk->header;
+	struct strbuf *plain = &s->plain;
+	size_t len = out->len, i;
+
+	strbuf_addf(out, " -%lu,%lu +%lu,%lu ",
+		    header->old_offset, header->old_count,
+		    header->new_offset, header->new_count);
+	if (out->len - len < SUMMARY_HEADER_WIDTH)
+		strbuf_addchars(out, ' ',
+				SUMMARY_HEADER_WIDTH + len - out->len);
+	for (i = hunk->start; i < hunk->end; i = find_next_line(plain, i))
+		if (plain->buf[i] != ' ')
+			break;
+	if (i < hunk->end)
+		strbuf_add(out, plain->buf + i, find_next_line(plain, i) - i);
+	if (out->len - len > SUMMARY_LINE_WIDTH)
+		strbuf_setlen(out, len + SUMMARY_LINE_WIDTH);
+	strbuf_complete_line(out);
+}
+
+#define DISPLAY_HUNKS_LINES 20
+static size_t display_hunks(struct add_p_state *s,
+			    struct file_diff *file_diff, size_t start_index)
+{
+	size_t end_index = start_index + DISPLAY_HUNKS_LINES;
+
+	if (end_index > file_diff->hunk_nr)
+		end_index = file_diff->hunk_nr;
+
+	while (start_index < end_index) {
+		struct hunk *hunk = file_diff->hunk + start_index++;
+
+		strbuf_reset(&s->buf);
+		strbuf_addf(&s->buf, "%c%2d: ", hunk->use == USE_HUNK ? '+'
+			    : hunk->use == SKIP_HUNK ? '-' : ' ',
+			    (int)start_index);
+		summarize_hunk(s, hunk, &s->buf);
+		fputs(s->buf.buf, stdout);
+	}
+
+	return end_index;
+}
+
 static const char help_patch_text[] =
 N_("y - stage this hunk\n"
    "n - do not stage this hunk\n"
@@ -964,6 +1012,7 @@ N_("y - stage this hunk\n"
    "J - leave this hunk undecided, see next hunk\n"
    "k - leave this hunk undecided, see previous undecided hunk\n"
    "K - leave this hunk undecided, see previous hunk\n"
+   "g - select a hunk to go to\n"
    "s - split the current hunk into smaller hunks\n"
    "e - manually edit the current hunk\n"
    "? - print help\n");
@@ -1022,6 +1071,8 @@ static int patch_update_file(struct add_p_state *s,
 			strbuf_addstr(&s->buf, ",j");
 		if (hunk_index + 1 < file_diff->hunk_nr)
 			strbuf_addstr(&s->buf, ",J");
+		if (file_diff->hunk_nr > 1)
+			strbuf_addstr(&s->buf, ",g");
 		if (hunk->splittable_into > 1)
 			strbuf_addstr(&s->buf, ",s");
 		if (hunk_index + 1 > file_diff->mode_change &&
@@ -1089,6 +1140,43 @@ soft_increment:
 				hunk_index = undecided_next;
 			else
 				err(s, _("No next hunk"));
+		} else if (s->answer.buf[0] == 'g') {
+			char *pend;
+			unsigned long response;
+
+			if (file_diff->hunk_nr < 2) {
+				err(s, _("No other hunks to goto"));
+				continue;
+			}
+			strbuf_remove(&s->answer, 0, 1);
+			strbuf_trim(&s->answer);
+			i = hunk_index - DISPLAY_HUNKS_LINES / 2;
+			if (i < file_diff->mode_change)
+				i = file_diff->mode_change;
+			while (s->answer.len == 0) {
+				i = display_hunks(s, file_diff, i);
+				printf("%s", i < file_diff->hunk_nr ?
+				       _("go to which hunk (<ret> to see "
+					 "more)? ") : _("go to which hunk? "));
+				fflush(stdout);
+				if (strbuf_getline(&s->answer,
+						   stdin) == EOF)
+					break;
+				strbuf_trim_trailing_newline(&s->answer);
+			}
+
+			strbuf_trim(&s->answer);
+			response = strtoul(s->answer.buf, &pend, 10);
+			if (*pend || pend == s->answer.buf)
+				err(s, _("Invalid number: '%s'"),
+				    s->answer.buf);
+			else if (0 < response && response <= file_diff->hunk_nr)
+				hunk_index = response - 1;
+			else
+				err(s, Q_("Sorry, only %d hunk available.",
+					  "Sorry, only %d hunks available.",
+					  file_diff->hunk_nr),
+				    (int)file_diff->hunk_nr);
 		} else if (s->answer.buf[0] == 's') {
 			size_t splittable_into = hunk->splittable_into;
 			if (splittable_into < 2)

t/t3701-add-interactive.sh

@@ -413,6 +413,22 @@ test_expect_success 'split hunk setup' '
 	test_write_lines 10 15 20 21 22 23 24 30 40 50 60 >test
 '
 
+test_expect_success 'goto hunk' '
+	test_when_finished "git reset" &&
+	tr _ " " >expect <<-EOF &&
+	(2/2) Stage this hunk [y,n,q,a,d,K,g,/,e,?]? + 1:  -1,2 +1,3          +15
+	_ 2:  -2,4 +3,8          +21
+	go to which hunk? @@ -1,2 +1,3 @@
+	_10
+	+15
+	_20
+	(1/2) Stage this hunk [y,n,q,a,d,j,J,g,/,e,?]?_
+	EOF
+	test_write_lines s y g 1 | git add -p >actual &&
+	tail -n 7 <actual >actual.trimmed &&
+	test_cmp expect actual.trimmed
+'
+
 test_expect_success 'split hunk "add -p (edit)"' '
 	# Split, say Edit and do nothing.  Then:
 	#