add-patch: update hunk splitability after editing

If, when the user edits a hunk, they change deletion lines into context lines or vice versa, then the number of hunks that the edited hunk can be split into may differ from the unedited hunk. This means that so we should recalculate `hunk->splittable_into` after the hunk has been edited. In practice users are unlikely to hit this bug as it is doubtful that a user who has edited a hunk will split it afterwards. Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Phillip Wood committed Sep 25, 2025 at 15:10 UTC 732650e263eb6bceda9988a8bbe75f311d908897
2 files changed +32 -1
add-patch.c
+11 -1
@@ -1185,19 +1185,29 @@ static ssize_t recount_edited_hunk(struct add_p_state *s, struct hunk *hunk,
1185 {
1186 struct hunk_header *header = &hunk->header;
1187 size_t i;
1188 + char ch, marker = ' ';
1189
1190 + hunk->splittable_into = 0;
1191 header->old_count = header->new_count = 0;
1192 for (i = hunk->start; i < hunk->end; ) {
1191 - switch(normalize_marker(&s->plain.buf[i])) {
1193 + ch = normalize_marker(&s->plain.buf[i]);
1194 + switch (ch) {
1195 case '-':
1196 header->old_count++;
1197 + if (marker == ' ')
1198 + hunk->splittable_into++;
1199 + marker = ch;
1200 break;
1201 case '+':
1202 header->new_count++;
1203 + if (marker == ' ')
1204 + hunk->splittable_into++;
1205 + marker = ch;
1206 break;
1207 case ' ':
1208 header->old_count++;
1209 header->new_count++;
1210 + marker = ch;
1211 break;
1212 }
1213
t/t3701-add-interactive.sh
+21
@@ -1311,4 +1311,25 @@ test_expect_success 'splitting previous hunk marks split hunks as undecided' '
1311 test_cmp expect actual
1312 '
1313
1314 +test_expect_success 'splitting edited hunk' '
1315 + # Before the first hunk is edited it can be split into two
1316 + # hunks, after editing it can be split into three hunks.
1317 +
1318 + write_script fake-editor.sh <<-\EOF &&
1319 + sed "s/^ c/-c/" "$1" >"$1.tmp" &&
1320 + mv "$1.tmp" "$1"
1321 + EOF
1322 +
1323 + test_write_lines a b c d e f g h i j k l m n >file &&
1324 + git add file &&
1325 + test_write_lines A b c d E f g h i j k l M n >file &&
1326 + (
1327 + test_set_editor "$(pwd)/fake-editor.sh" &&
1328 + test_write_lines e K s j y n y q | git add -p file
1329 + ) &&
1330 + git cat-file blob :file >actual &&
1331 + test_write_lines a b d e f g h i j k l M n >expect &&
1332 + test_cmp expect actual
1333 +'
1334 +
1335 test_done