merge(3p/git): Merge git upstream at v2.26.2 r/808

1 files changed, 1683 insertions, 0 deletions

diff --git a/third_party/git/add-patch.c b/third_party/git/add-patch.c
new file mode 100644
index 000000000000..d8dafa8168dc
--- /dev/null
+++ b/third_party/git/add-patch.c
@@ -0,0 +1,1683 @@
+#include "cache.h"
+#include "add-interactive.h"
+#include "strbuf.h"
+#include "run-command.h"
+#include "argv-array.h"
+#include "pathspec.h"
+#include "color.h"
+#include "diff.h"
+#include "compat/terminal.h"
+
+enum prompt_mode_type {
+	PROMPT_MODE_CHANGE = 0, PROMPT_DELETION, PROMPT_HUNK,
+	PROMPT_MODE_MAX, /* must be last */
+};
+
+struct patch_mode {
+	/*
+	 * The magic constant 4 is chosen such that all patch modes
+	 * provide enough space for three command-line arguments followed by a
+	 * trailing `NULL`.
+	 */
+	const char *diff_cmd[4], *apply_args[4], *apply_check_args[4];
+	unsigned is_reverse:1, index_only:1, apply_for_checkout:1;
+	const char *prompt_mode[PROMPT_MODE_MAX];
+	const char *edit_hunk_hint, *help_patch_text;
+};
+
+static struct patch_mode patch_mode_add = {
+	.diff_cmd = { "diff-files", NULL },
+	.apply_args = { "--cached", NULL },
+	.apply_check_args = { "--cached", NULL },
+	.prompt_mode = {
+		N_("Stage mode change [y,n,q,a,d%s,?]? "),
+		N_("Stage deletion [y,n,q,a,d%s,?]? "),
+		N_("Stage this hunk [y,n,q,a,d%s,?]? ")
+	},
+	.edit_hunk_hint = N_("If the patch applies cleanly, the edited hunk "
+			     "will immediately be marked for staging."),
+	.help_patch_text =
+		N_("y - stage this hunk\n"
+		   "n - do not stage this hunk\n"
+		   "q - quit; do not stage this hunk or any of the remaining "
+			"ones\n"
+		   "a - stage this hunk and all later hunks in the file\n"
+		   "d - do not stage this hunk or any of the later hunks in "
+			"the file\n")
+};
+
+static struct patch_mode patch_mode_stash = {
+	.diff_cmd = { "diff-index", "HEAD", NULL },
+	.apply_args = { "--cached", NULL },
+	.apply_check_args = { "--cached", NULL },
+	.prompt_mode = {
+		N_("Stash mode change [y,n,q,a,d%s,?]? "),
+		N_("Stash deletion [y,n,q,a,d%s,?]? "),
+		N_("Stash this hunk [y,n,q,a,d%s,?]? "),
+	},
+	.edit_hunk_hint = N_("If the patch applies cleanly, the edited hunk "
+			     "will immediately be marked for stashing."),
+	.help_patch_text =
+		N_("y - stash this hunk\n"
+		   "n - do not stash this hunk\n"
+		   "q - quit; do not stash this hunk or any of the remaining "
+			"ones\n"
+		   "a - stash this hunk and all later hunks in the file\n"
+		   "d - do not stash this hunk or any of the later hunks in "
+			"the file\n"),
+};
+
+static struct patch_mode patch_mode_reset_head = {
+	.diff_cmd = { "diff-index", "--cached", NULL },
+	.apply_args = { "-R", "--cached", NULL },
+	.apply_check_args = { "-R", "--cached", NULL },
+	.is_reverse = 1,
+	.index_only = 1,
+	.prompt_mode = {
+		N_("Unstage mode change [y,n,q,a,d%s,?]? "),
+		N_("Unstage deletion [y,n,q,a,d%s,?]? "),
+		N_("Unstage this hunk [y,n,q,a,d%s,?]? "),
+	},
+	.edit_hunk_hint = N_("If the patch applies cleanly, the edited hunk "
+			     "will immediately be marked for unstaging."),
+	.help_patch_text =
+		N_("y - unstage this hunk\n"
+		   "n - do not unstage this hunk\n"
+		   "q - quit; do not unstage this hunk or any of the remaining "
+			"ones\n"
+		   "a - unstage this hunk and all later hunks in the file\n"
+		   "d - do not unstage this hunk or any of the later hunks in "
+			"the file\n"),
+};
+
+static struct patch_mode patch_mode_reset_nothead = {
+	.diff_cmd = { "diff-index", "-R", "--cached", NULL },
+	.apply_args = { "--cached", NULL },
+	.apply_check_args = { "--cached", NULL },
+	.index_only = 1,
+	.prompt_mode = {
+		N_("Apply mode change to index [y,n,q,a,d%s,?]? "),
+		N_("Apply deletion to index [y,n,q,a,d%s,?]? "),
+		N_("Apply this hunk to index [y,n,q,a,d%s,?]? "),
+	},
+	.edit_hunk_hint = N_("If the patch applies cleanly, the edited hunk "
+			     "will immediately be marked for applying."),
+	.help_patch_text =
+		N_("y - apply this hunk to index\n"
+		   "n - do not apply this hunk to index\n"
+		   "q - quit; do not apply this hunk or any of the remaining "
+			"ones\n"
+		   "a - apply this hunk and all later hunks in the file\n"
+		   "d - do not apply this hunk or any of the later hunks in "
+			"the file\n"),
+};
+
+static struct patch_mode patch_mode_checkout_index = {
+	.diff_cmd = { "diff-files", NULL },
+	.apply_args = { "-R", NULL },
+	.apply_check_args = { "-R", NULL },
+	.is_reverse = 1,
+	.prompt_mode = {
+		N_("Discard mode change from worktree [y,n,q,a,d%s,?]? "),
+		N_("Discard deletion from worktree [y,n,q,a,d%s,?]? "),
+		N_("Discard this hunk from worktree [y,n,q,a,d%s,?]? "),
+	},
+	.edit_hunk_hint = N_("If the patch applies cleanly, the edited hunk "
+			     "will immediately be marked for discarding."),
+	.help_patch_text =
+		N_("y - discard this hunk from worktree\n"
+		   "n - do not discard this hunk from worktree\n"
+		   "q - quit; do not discard this hunk or any of the remaining "
+			"ones\n"
+		   "a - discard this hunk and all later hunks in the file\n"
+		   "d - do not discard this hunk or any of the later hunks in "
+			"the file\n"),
+};
+
+static struct patch_mode patch_mode_checkout_head = {
+	.diff_cmd = { "diff-index", NULL },
+	.apply_for_checkout = 1,
+	.apply_check_args = { "-R", NULL },
+	.is_reverse = 1,
+	.prompt_mode = {
+		N_("Discard mode change from index and worktree [y,n,q,a,d%s,?]? "),
+		N_("Discard deletion from index and worktree [y,n,q,a,d%s,?]? "),
+		N_("Discard this hunk from index and worktree [y,n,q,a,d%s,?]? "),
+	},
+	.edit_hunk_hint = N_("If the patch applies cleanly, the edited hunk "
+			     "will immediately be marked for discarding."),
+	.help_patch_text =
+		N_("y - discard this hunk from index and worktree\n"
+		   "n - do not discard this hunk from index and worktree\n"
+		   "q - quit; do not discard this hunk or any of the remaining "
+			"ones\n"
+		   "a - discard this hunk and all later hunks in the file\n"
+		   "d - do not discard this hunk or any of the later hunks in "
+			"the file\n"),
+};
+
+static struct patch_mode patch_mode_checkout_nothead = {
+	.diff_cmd = { "diff-index", "-R", NULL },
+	.apply_for_checkout = 1,
+	.apply_check_args = { NULL },
+	.prompt_mode = {
+		N_("Apply mode change to index and worktree [y,n,q,a,d%s,?]? "),
+		N_("Apply deletion to index and worktree [y,n,q,a,d%s,?]? "),
+		N_("Apply this hunk to index and worktree [y,n,q,a,d%s,?]? "),
+	},
+	.edit_hunk_hint = N_("If the patch applies cleanly, the edited hunk "
+			     "will immediately be marked for applying."),
+	.help_patch_text =
+		N_("y - apply this hunk to index and worktree\n"
+		   "n - do not apply this hunk to index and worktree\n"
+		   "q - quit; do not apply this hunk or any of the remaining "
+			"ones\n"
+		   "a - apply this hunk and all later hunks in the file\n"
+		   "d - do not apply this hunk or any of the later hunks in "
+			"the file\n"),
+};
+
+static struct patch_mode patch_mode_worktree_head = {
+	.diff_cmd = { "diff-index", NULL },
+	.apply_args = { "-R", NULL },
+	.apply_check_args = { "-R", NULL },
+	.is_reverse = 1,
+	.prompt_mode = {
+		N_("Discard mode change from index and worktree [y,n,q,a,d%s,?]? "),
+		N_("Discard deletion from index and worktree [y,n,q,a,d%s,?]? "),
+		N_("Discard this hunk from index and worktree [y,n,q,a,d%s,?]? "),
+	},
+	.edit_hunk_hint = N_("If the patch applies cleanly, the edited hunk "
+			     "will immediately be marked for discarding."),
+	.help_patch_text =
+		N_("y - discard this hunk from worktree\n"
+		   "n - do not discard this hunk from worktree\n"
+		   "q - quit; do not discard this hunk or any of the remaining "
+			"ones\n"
+		   "a - discard this hunk and all later hunks in the file\n"
+		   "d - do not discard this hunk or any of the later hunks in "
+			"the file\n"),
+};
+
+static struct patch_mode patch_mode_worktree_nothead = {
+	.diff_cmd = { "diff-index", "-R", NULL },
+	.apply_args = { NULL },
+	.apply_check_args = { NULL },
+	.prompt_mode = {
+		N_("Apply mode change to index and worktree [y,n,q,a,d%s,?]? "),
+		N_("Apply deletion to index and worktree [y,n,q,a,d%s,?]? "),
+		N_("Apply this hunk to index and worktree [y,n,q,a,d%s,?]? "),
+	},
+	.edit_hunk_hint = N_("If the patch applies cleanly, the edited hunk "
+			     "will immediately be marked for applying."),
+	.help_patch_text =
+		N_("y - apply this hunk to worktree\n"
+		   "n - do not apply this hunk to worktree\n"
+		   "q - quit; do not apply this hunk or any of the remaining "
+			"ones\n"
+		   "a - apply this hunk and all later hunks in the file\n"
+		   "d - do not apply this hunk or any of the later hunks in "
+			"the file\n"),
+};
+
+struct hunk_header {
+	unsigned long old_offset, old_count, new_offset, new_count;
+	/*
+	 * Start/end offsets to the extra text after the second `@@` in the
+	 * hunk header, e.g. the function signature. This is expected to
+	 * include the newline.
+	 */
+	size_t extra_start, extra_end, colored_extra_start, colored_extra_end;
+};
+
+struct hunk {
+	size_t start, end, colored_start, colored_end, splittable_into;
+	ssize_t delta;
+	enum { UNDECIDED_HUNK = 0, SKIP_HUNK, USE_HUNK } use;
+	struct hunk_header header;
+};
+
+struct add_p_state {
+	struct add_i_state s;
+	struct strbuf answer, buf;
+
+	/* parsed diff */
+	struct strbuf plain, colored;
+	struct file_diff {
+		struct hunk head;
+		struct hunk *hunk;
+		size_t hunk_nr, hunk_alloc;
+		unsigned deleted:1, mode_change:1,binary:1;
+	} *file_diff;
+	size_t file_diff_nr;
+
+	/* patch mode */
+	struct patch_mode *mode;
+	const char *revision;
+};
+
+static void err(struct add_p_state *s, const char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	fputs(s->s.error_color, stderr);
+	vfprintf(stderr, fmt, args);
+	fputs(s->s.reset_color, stderr);
+	fputc('\n', stderr);
+	va_end(args);
+}
+
+static void setup_child_process(struct add_p_state *s,
+				struct child_process *cp, ...)
+{
+	va_list ap;
+	const char *arg;
+
+	va_start(ap, cp);
+	while ((arg = va_arg(ap, const char *)))
+		argv_array_push(&cp->args, arg);
+	va_end(ap);
+
+	cp->git_cmd = 1;
+	argv_array_pushf(&cp->env_array,
+			 INDEX_ENVIRONMENT "=%s", s->s.r->index_file);
+}
+
+static int parse_range(const char **p,
+		       unsigned long *offset, unsigned long *count)
+{
+	char *pend;
+
+	*offset = strtoul(*p, &pend, 10);
+	if (pend == *p)
+		return -1;
+	if (*pend != ',') {
+		*count = 1;
+		*p = pend;
+		return 0;
+	}
+	*count = strtoul(pend + 1, (char **)p, 10);
+	return *p == pend + 1 ? -1 : 0;
+}
+
+static int parse_hunk_header(struct add_p_state *s, struct hunk *hunk)
+{
+	struct hunk_header *header = &hunk->header;
+	const char *line = s->plain.buf + hunk->start, *p = line;
+	char *eol = memchr(p, '\n', s->plain.len - hunk->start);
+
+	if (!eol)
+		eol = s->plain.buf + s->plain.len;
+
+	if (!skip_prefix(p, "@@ -", &p) ||
+	    parse_range(&p, &header->old_offset, &header->old_count) < 0 ||
+	    !skip_prefix(p, " +", &p) ||
+	    parse_range(&p, &header->new_offset, &header->new_count) < 0 ||
+	    !skip_prefix(p, " @@", &p))
+		return error(_("could not parse hunk header '%.*s'"),
+			     (int)(eol - line), line);
+
+	hunk->start = eol - s->plain.buf + (*eol == '\n');
+	header->extra_start = p - s->plain.buf;
+	header->extra_end = hunk->start;
+
+	if (!s->colored.len) {
+		header->colored_extra_start = header->colored_extra_end = 0;
+		return 0;
+	}
+
+	/* Now find the extra text in the colored diff */
+	line = s->colored.buf + hunk->colored_start;
+	eol = memchr(line, '\n', s->colored.len - hunk->colored_start);
+	if (!eol)
+		eol = s->colored.buf + s->colored.len;
+	p = memmem(line, eol - line, "@@ -", 4);
+	if (!p)
+		return error(_("could not parse colored hunk header '%.*s'"),
+			     (int)(eol - line), line);
+	p = memmem(p + 4, eol - p - 4, " @@", 3);
+	if (!p)
+		return error(_("could not parse colored hunk header '%.*s'"),
+			     (int)(eol - line), line);
+	hunk->colored_start = eol - s->colored.buf + (*eol == '\n');
+	header->colored_extra_start = p + 3 - s->colored.buf;
+	header->colored_extra_end = hunk->colored_start;
+
+	return 0;
+}
+
+static int is_octal(const char *p, size_t len)
+{
+	if (!len)
+		return 0;
+
+	while (len--)
+		if (*p < '0' || *(p++) > '7')
+			return 0;
+	return 1;
+}
+
+static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
+{
+	struct argv_array args = ARGV_ARRAY_INIT;
+	const char *diff_algorithm = s->s.interactive_diff_algorithm;
+	struct strbuf *plain = &s->plain, *colored = NULL;
+	struct child_process cp = CHILD_PROCESS_INIT;
+	char *p, *pend, *colored_p = NULL, *colored_pend = NULL, marker = '\0';
+	size_t file_diff_alloc = 0, i, color_arg_index;
+	struct file_diff *file_diff = NULL;
+	struct hunk *hunk = NULL;
+	int res;
+
+	argv_array_pushv(&args, s->mode->diff_cmd);
+	if (diff_algorithm)
+		argv_array_pushf(&args, "--diff-algorithm=%s", diff_algorithm);
+	if (s->revision) {
+		struct object_id oid;
+		argv_array_push(&args,
+				/* could be on an unborn branch */
+				!strcmp("HEAD", s->revision) &&
+				get_oid("HEAD", &oid) ?
+				empty_tree_oid_hex() : s->revision);
+	}
+	color_arg_index = args.argc;
+	/* Use `--no-color` explicitly, just in case `diff.color = always`. */
+	argv_array_pushl(&args, "--no-color", "-p", "--", NULL);
+	for (i = 0; i < ps->nr; i++)
+		argv_array_push(&args, ps->items[i].original);
+
+	setup_child_process(s, &cp, NULL);
+	cp.argv = args.argv;
+	res = capture_command(&cp, plain, 0);
+	if (res) {
+		argv_array_clear(&args);
+		return error(_("could not parse diff"));
+	}
+	if (!plain->len) {
+		argv_array_clear(&args);
+		return 0;
+	}
+	strbuf_complete_line(plain);
+
+	if (want_color_fd(1, -1)) {
+		struct child_process colored_cp = CHILD_PROCESS_INIT;
+		const char *diff_filter = s->s.interactive_diff_filter;
+
+		setup_child_process(s, &colored_cp, NULL);
+		xsnprintf((char *)args.argv[color_arg_index], 8, "--color");
+		colored_cp.argv = args.argv;
+		colored = &s->colored;
+		res = capture_command(&colored_cp, colored, 0);
+		argv_array_clear(&args);
+		if (res)
+			return error(_("could not parse colored diff"));
+
+		if (diff_filter) {
+			struct child_process filter_cp = CHILD_PROCESS_INIT;
+
+			setup_child_process(s, &filter_cp,
+					    diff_filter, NULL);
+			filter_cp.git_cmd = 0;
+			filter_cp.use_shell = 1;
+			strbuf_reset(&s->buf);
+			if (pipe_command(&filter_cp,
+					 colored->buf, colored->len,
+					 &s->buf, colored->len,
+					 NULL, 0) < 0)
+				return error(_("failed to run '%s'"),
+					     diff_filter);
+			strbuf_swap(colored, &s->buf);
+		}
+
+		strbuf_complete_line(colored);
+		colored_p = colored->buf;
+		colored_pend = colored_p + colored->len;
+	}
+	argv_array_clear(&args);
+
+	/* parse files and hunks */
+	p = plain->buf;
+	pend = p + plain->len;
+	while (p != pend) {
+		char *eol = memchr(p, '\n', pend - p);
+		const char *deleted = NULL, *mode_change = NULL;
+
+		if (!eol)
+			eol = pend;
+
+		if (starts_with(p, "diff ")) {
+			s->file_diff_nr++;
+			ALLOC_GROW(s->file_diff, s->file_diff_nr,
+				   file_diff_alloc);
+			file_diff = s->file_diff + s->file_diff_nr - 1;
+			memset(file_diff, 0, sizeof(*file_diff));
+			hunk = &file_diff->head;
+			hunk->start = p - plain->buf;
+			if (colored_p)
+				hunk->colored_start = colored_p - colored->buf;
+			marker = '\0';
+		} else if (p == plain->buf)
+			BUG("diff starts with unexpected line:\n"
+			    "%.*s\n", (int)(eol - p), p);
+		else if (file_diff->deleted)
+			; /* keep the rest of the file in a single "hunk" */
+		else if (starts_with(p, "@@ ") ||
+			 (hunk == &file_diff->head &&
+			  skip_prefix(p, "deleted file", &deleted))) {
+			if (marker == '-' || marker == '+')
+				/*
+				 * Should not happen; previous hunk did not end
+				 * in a context line? Handle it anyway.
+				 */
+				hunk->splittable_into++;
+
+			file_diff->hunk_nr++;
+			ALLOC_GROW(file_diff->hunk, file_diff->hunk_nr,
+				   file_diff->hunk_alloc);
+			hunk = file_diff->hunk + file_diff->hunk_nr - 1;
+			memset(hunk, 0, sizeof(*hunk));
+
+			hunk->start = p - plain->buf;
+			if (colored)
+				hunk->colored_start = colored_p - colored->buf;
+
+			if (deleted)
+				file_diff->deleted = 1;
+			else if (parse_hunk_header(s, hunk) < 0)
+				return -1;
+
+			/*
+			 * Start counting into how many hunks this one can be
+			 * split
+			 */
+			marker = *p;
+		} else if (hunk == &file_diff->head &&
+			   skip_prefix(p, "old mode ", &mode_change) &&
+			   is_octal(mode_change, eol - mode_change)) {
+			if (file_diff->mode_change)
+				BUG("double mode change?\n\n%.*s",
+				    (int)(eol - plain->buf), plain->buf);
+			if (file_diff->hunk_nr++)
+				BUG("mode change in the middle?\n\n%.*s",
+				    (int)(eol - plain->buf), plain->buf);
+
+			/*
+			 * Do *not* change `hunk`: the mode change pseudo-hunk
+			 * is _part of_ the header "hunk".
+			 */
+			file_diff->mode_change = 1;
+			ALLOC_GROW(file_diff->hunk, file_diff->hunk_nr,
+				   file_diff->hunk_alloc);
+			memset(file_diff->hunk, 0, sizeof(struct hunk));
+			file_diff->hunk->start = p - plain->buf;
+			if (colored_p)
+				file_diff->hunk->colored_start =
+					colored_p - colored->buf;
+		} else if (hunk == &file_diff->head &&
+			   skip_prefix(p, "new mode ", &mode_change) &&
+			   is_octal(mode_change, eol - mode_change)) {
+
+			/*
+			 * Extend the "mode change" pseudo-hunk to include also
+			 * the "new mode" line.
+			 */
+			if (!file_diff->mode_change)
+				BUG("'new mode' without 'old mode'?\n\n%.*s",
+				    (int)(eol - plain->buf), plain->buf);
+			if (file_diff->hunk_nr != 1)
+				BUG("mode change in the middle?\n\n%.*s",
+				    (int)(eol - plain->buf), plain->buf);
+			if (p - plain->buf != file_diff->hunk->end)
+				BUG("'new mode' does not immediately follow "
+				    "'old mode'?\n\n%.*s",
+				    (int)(eol - plain->buf), plain->buf);
+		} else if (hunk == &file_diff->head &&
+			   starts_with(p, "Binary files "))
+			file_diff->binary = 1;
+
+		if (file_diff->deleted && file_diff->mode_change)
+			BUG("diff contains delete *and* a mode change?!?\n%.*s",
+			    (int)(eol - (plain->buf + file_diff->head.start)),
+			    plain->buf + file_diff->head.start);
+
+		if ((marker == '-' || marker == '+') && *p == ' ')
+			hunk->splittable_into++;
+		if (marker && *p != '\\')
+			marker = *p;
+
+		p = eol == pend ? pend : eol + 1;
+		hunk->end = p - plain->buf;
+
+		if (colored) {
+			char *colored_eol = memchr(colored_p, '\n',
+						   colored_pend - colored_p);
+			if (colored_eol)
+				colored_p = colored_eol + 1;
+			else if (p != pend)
+				/* colored shorter than non-colored? */
+				goto mismatched_output;
+			else
+				colored_p = colored_pend;
+
+			hunk->colored_end = colored_p - colored->buf;
+		}
+
+		if (mode_change) {
+			if (file_diff->hunk_nr != 1)
+				BUG("mode change in hunk #%d???",
+				    (int)file_diff->hunk_nr);
+			/* Adjust the end of the "mode change" pseudo-hunk */
+			file_diff->hunk->end = hunk->end;
+			if (colored)
+				file_diff->hunk->colored_end = hunk->colored_end;
+		}
+	}
+
+	if (marker == '-' || marker == '+')
+		/*
+		 * Last hunk ended in non-context line (i.e. it appended lines
+		 * to the file, so there are no trailing context lines).
+		 */
+		hunk->splittable_into++;
+
+	/* non-colored shorter than colored? */
+	if (colored_p != colored_pend) {
+mismatched_output:
+		error(_("mismatched output from interactive.diffFilter"));
+		advise(_("Your filter must maintain a one-to-one correspondence\n"
+			 "between its input and output lines."));
+		return -1;
+	}
+
+	return 0;
+}
+
+static size_t find_next_line(struct strbuf *sb, size_t offset)
+{
+	char *eol;
+
+	if (offset >= sb->len)
+		BUG("looking for next line beyond buffer (%d >= %d)\n%s",
+		    (int)offset, (int)sb->len, sb->buf);
+
+	eol = memchr(sb->buf + offset, '\n', sb->len - offset);
+	if (!eol)
+		return sb->len;
+	return eol - sb->buf + 1;
+}
+
+static void render_hunk(struct add_p_state *s, struct hunk *hunk,
+			ssize_t delta, int colored, struct strbuf *out)
+{
+	struct hunk_header *header = &hunk->header;
+
+	if (hunk->header.old_offset != 0 || hunk->header.new_offset != 0) {
+		/*
+		 * Generate the hunk header dynamically, except for special
+		 * hunks (such as the diff header).
+		 */
+		const char *p;
+		size_t len;
+		unsigned long old_offset = header->old_offset;
+		unsigned long new_offset = header->new_offset;
+
+		if (!colored) {
+			p = s->plain.buf + header->extra_start;
+			len = header->extra_end - header->extra_start;
+		} else {
+			strbuf_addstr(out, s->s.fraginfo_color);
+			p = s->colored.buf + header->colored_extra_start;
+			len = header->colored_extra_end
+				- header->colored_extra_start;
+		}
+
+		if (s->mode->is_reverse)
+			old_offset -= delta;
+		else
+			new_offset += delta;
+
+		strbuf_addf(out, "@@ -%lu,%lu +%lu,%lu @@",
+			    old_offset, header->old_count,
+			    new_offset, header->new_count);
+		if (len)
+			strbuf_add(out, p, len);
+		else if (colored)
+			strbuf_addf(out, "%s\n", GIT_COLOR_RESET);
+		else
+			strbuf_addch(out, '\n');
+	}
+
+	if (colored)
+		strbuf_add(out, s->colored.buf + hunk->colored_start,
+			   hunk->colored_end - hunk->colored_start);
+	else
+		strbuf_add(out, s->plain.buf + hunk->start,
+			   hunk->end - hunk->start);
+}
+
+static void render_diff_header(struct add_p_state *s,
+			       struct file_diff *file_diff, int colored,
+			       struct strbuf *out)
+{
+	/*
+	 * If there was a mode change, the first hunk is a pseudo hunk that
+	 * corresponds to the mode line in the header. If the user did not want
+	 * to stage that "hunk", we actually have to cut it out from the header.
+	 */
+	int skip_mode_change =
+		file_diff->mode_change && file_diff->hunk->use != USE_HUNK;
+	struct hunk *head = &file_diff->head, *first = file_diff->hunk;
+
+	if (!skip_mode_change) {
+		render_hunk(s, head, 0, colored, out);
+		return;
+	}
+
+	if (colored) {
+		const char *p = s->colored.buf;
+
+		strbuf_add(out, p + head->colored_start,
+			    first->colored_start - head->colored_start);
+		strbuf_add(out, p + first->colored_end,
+			    head->colored_end - first->colored_end);
+	} else {
+		const char *p = s->plain.buf;
+
+		strbuf_add(out, p + head->start, first->start - head->start);
+		strbuf_add(out, p + first->end, head->end - first->end);
+	}
+}
+
+/* Coalesce hunks again that were split */
+static int merge_hunks(struct add_p_state *s, struct file_diff *file_diff,
+		       size_t *hunk_index, int use_all, struct hunk *merged)
+{
+	size_t i = *hunk_index, delta;
+	struct hunk *hunk = file_diff->hunk + i;
+	/* `header` corresponds to the merged hunk */
+	struct hunk_header *header = &merged->header, *next;
+
+	if (!use_all && hunk->use != USE_HUNK)
+		return 0;
+
+	*merged = *hunk;
+	/* We simply skip the colored part (if any) when merging hunks */
+	merged->colored_start = merged->colored_end = 0;
+
+	for (; i + 1 < file_diff->hunk_nr; i++) {
+		hunk++;
+		next = &hunk->header;
+
+		/*
+		 * Stop merging hunks when:
+		 *
+		 * - the hunk is not selected for use, or
+		 * - the hunk does not overlap with the already-merged hunk(s)
+		 */
+		if ((!use_all && hunk->use != USE_HUNK) ||
+		    header->new_offset >= next->new_offset + merged->delta ||
+		    header->new_offset + header->new_count
+		    < next->new_offset + merged->delta)
+			break;
+
+		/*
+		 * If the hunks were not edited, and overlap, we can simply
+		 * extend the line range.
+		 */
+		if (merged->start < hunk->start && merged->end > hunk->start) {
+			merged->end = hunk->end;
+			merged->colored_end = hunk->colored_end;
+			delta = 0;
+		} else {
+			const char *plain = s->plain.buf;
+			size_t  overlapping_line_count = header->new_offset
+				+ header->new_count - merged->delta
+				- next->new_offset;
+			size_t overlap_end = hunk->start;
+			size_t overlap_start = overlap_end;
+			size_t overlap_next, len, j;
+
+			/*
+			 * One of the hunks was edited: the modified hunk was
+			 * appended to the strbuf `s->plain`.
+			 *
+			 * Let's ensure that at least the last context line of
+			 * the first hunk overlaps with the corresponding line
+			 * of the second hunk, and then merge.
+			 */
+			for (j = 0; j < overlapping_line_count; j++) {
+				overlap_next = find_next_line(&s->plain,
+							      overlap_end);
+
+				if (overlap_next > hunk->end)
+					BUG("failed to find %d context lines "
+					    "in:\n%.*s",
+					    (int)overlapping_line_count,
+					    (int)(hunk->end - hunk->start),
+					    plain + hunk->start);
+
+				if (plain[overlap_end] != ' ')
+					return error(_("expected context line "
+						       "#%d in\n%.*s"),
+						     (int)(j + 1),
+						     (int)(hunk->end
+							   - hunk->start),
+						     plain + hunk->start);
+
+				overlap_start = overlap_end;
+				overlap_end = overlap_next;
+			}
+			len = overlap_end - overlap_start;
+
+			if (len > merged->end - merged->start ||
+			    memcmp(plain + merged->end - len,
+				   plain + overlap_start, len))
+				return error(_("hunks do not overlap:\n%.*s\n"
+					       "\tdoes not end with:\n%.*s"),
+					     (int)(merged->end - merged->start),
+					     plain + merged->start,
+					     (int)len, plain + overlap_start);
+
+			/*
+			 * Since the start-end ranges are not adjacent, we
+			 * cannot simply take the union of the ranges. To
+			 * address that, we temporarily append the union of the
+			 * lines to the `plain` strbuf.
+			 */
+			if (merged->end != s->plain.len) {
+				size_t start = s->plain.len;
+
+				strbuf_add(&s->plain, plain + merged->start,
+					   merged->end - merged->start);
+				plain = s->plain.buf;
+				merged->start = start;
+				merged->end = s->plain.len;
+			}
+
+			strbuf_add(&s->plain,
+				   plain + overlap_end,
+				   hunk->end - overlap_end);
+			merged->end = s->plain.len;
+			merged->splittable_into += hunk->splittable_into;
+			delta = merged->delta;
+			merged->delta += hunk->delta;
+		}
+
+		header->old_count = next->old_offset + next->old_count
+			- header->old_offset;
+		header->new_count = next->new_offset + delta
+			+ next->new_count - header->new_offset;
+	}
+
+	if (i == *hunk_index)
+		return 0;
+
+	*hunk_index = i;
+	return 1;
+}
+
+static void reassemble_patch(struct add_p_state *s,
+			     struct file_diff *file_diff, int use_all,
+			     struct strbuf *out)
+{
+	struct hunk *hunk;
+	size_t save_len = s->plain.len, i;
+	ssize_t delta = 0;
+
+	render_diff_header(s, file_diff, 0, out);
+
+	for (i = file_diff->mode_change; i < file_diff->hunk_nr; i++) {
+		struct hunk merged = { 0 };
+
+		hunk = file_diff->hunk + i;
+		if (!use_all && hunk->use != USE_HUNK)
+			delta += hunk->header.old_count
+				- hunk->header.new_count;
+		else {
+			/* merge overlapping hunks into a temporary hunk */
+			if (merge_hunks(s, file_diff, &i, use_all, &merged))
+				hunk = &merged;
+
+			render_hunk(s, hunk, delta, 0, out);
+
+			/*
+			 * In case `merge_hunks()` used `plain` as a scratch
+			 * pad (this happens when an edited hunk had to be
+			 * coalesced with another hunk).
+			 */
+			strbuf_setlen(&s->plain, save_len);
+
+			delta += hunk->delta;
+		}
+	}
+}
+
+static int split_hunk(struct add_p_state *s, struct file_diff *file_diff,
+		       size_t hunk_index)
+{
+	int colored = !!s->colored.len, first = 1;
+	struct hunk *hunk = file_diff->hunk + hunk_index;
+	size_t splittable_into;
+	size_t end, colored_end, current, colored_current = 0, context_line_count;
+	struct hunk_header remaining, *header;
+	char marker, ch;
+
+	if (hunk_index >= file_diff->hunk_nr)
+		BUG("invalid hunk index: %d (must be >= 0 and < %d)",
+		    (int)hunk_index, (int)file_diff->hunk_nr);
+
+	if (hunk->splittable_into < 2)
+		return 0;
+	splittable_into = hunk->splittable_into;
+
+	end = hunk->end;
+	colored_end = hunk->colored_end;
+
+	remaining = hunk->header;
+
+	file_diff->hunk_nr += splittable_into - 1;
+	ALLOC_GROW(file_diff->hunk, file_diff->hunk_nr, file_diff->hunk_alloc);
+	if (hunk_index + splittable_into < file_diff->hunk_nr)
+		memmove(file_diff->hunk + hunk_index + splittable_into,
+			file_diff->hunk + hunk_index + 1,
+			(file_diff->hunk_nr - hunk_index - splittable_into)
+			* sizeof(*hunk));
+	hunk = file_diff->hunk + hunk_index;
+	hunk->splittable_into = 1;
+	memset(hunk + 1, 0, (splittable_into - 1) * sizeof(*hunk));
+
+	header = &hunk->header;
+	header->old_count = header->new_count = 0;
+
+	current = hunk->start;
+	if (colored)
+		colored_current = hunk->colored_start;
+	marker = '\0';
+	context_line_count = 0;
+
+	while (splittable_into > 1) {
+		ch = s->plain.buf[current];
+
+		if (!ch)
+			BUG("buffer overrun while splitting hunks");
+
+		/*
+		 * Is this the first context line after a chain of +/- lines?
+		 * Then record the start of the next split hunk.
+		 */
+		if ((marker == '-' || marker == '+') && ch == ' ') {
+			first = 0;
+			hunk[1].start = current;
+			if (colored)
+				hunk[1].colored_start = colored_current;
+			context_line_count = 0;
+		}
+
+		/*
+		 * Was the previous line a +/- one? Alternatively, is this the
+		 * first line (and not a +/- one)?
+		 *
+		 * Then just increment the appropriate counter and continue
+		 * with the next line.
+		 */
+		if (marker != ' ' || (ch != '-' && ch != '+')) {
+next_hunk_line:
+			/* Comment lines are attached to the previous line */
+			if (ch == '\\')
+				ch = marker ? marker : ' ';
+
+			/* current hunk not done yet */
+			if (ch == ' ')
+				context_line_count++;
+			else if (ch == '-')
+				header->old_count++;
+			else if (ch == '+')
+				header->new_count++;
+			else
+				BUG("unhandled diff marker: '%c'", ch);
+			marker = ch;
+			current = find_next_line(&s->plain, current);
+			if (colored)
+				colored_current =
+					find_next_line(&s->colored,
+						       colored_current);
+			continue;
+		}
+
+		/*
+		 * We got us the start of a new hunk!
+		 *
+		 * This is a context line, so it is shared with the previous
+		 * hunk, if any.
+		 */
+
+		if (first) {
+			if (header->old_count || header->new_count)
+				BUG("counts are off: %d/%d",
+				    (int)header->old_count,
+				    (int)header->new_count);
+
+			header->old_count = context_line_count;
+			header->new_count = context_line_count;
+			context_line_count = 0;
+			first = 0;
+			goto next_hunk_line;
+		}
+
+		remaining.old_offset += header->old_count;
+		remaining.old_count -= header->old_count;
+		remaining.new_offset += header->new_count;
+		remaining.new_count -= header->new_count;
+
+		/* initialize next hunk header's offsets */
+		hunk[1].header.old_offset =
+			header->old_offset + header->old_count;
+		hunk[1].header.new_offset =
+			header->new_offset + header->new_count;
+
+		/* add one split hunk */
+		header->old_count += context_line_count;
+		header->new_count += context_line_count;
+
+		hunk->end = current;
+		if (colored)
+			hunk->colored_end = colored_current;
+
+		hunk++;
+		hunk->splittable_into = 1;
+		hunk->use = hunk[-1].use;
+		header = &hunk->header;
+
+		header->old_count = header->new_count = context_line_count;
+		context_line_count = 0;
+
+		splittable_into--;
+		marker = ch;
+	}
+
+	/* last hunk simply gets the rest */
+	if (header->old_offset != remaining.old_offset)
+		BUG("miscounted old_offset: %lu != %lu",
+		    header->old_offset, remaining.old_offset);
+	if (header->new_offset != remaining.new_offset)
+		BUG("miscounted new_offset: %lu != %lu",
+		    header->new_offset, remaining.new_offset);
+	header->old_count = remaining.old_count;
+	header->new_count = remaining.new_count;
+	hunk->end = end;
+	if (colored)
+		hunk->colored_end = colored_end;
+
+	return 0;
+}
+
+static void recolor_hunk(struct add_p_state *s, struct hunk *hunk)
+{
+	const char *plain = s->plain.buf;
+	size_t current, eol, next;
+
+	if (!s->colored.len)
+		return;
+
+	hunk->colored_start = s->colored.len;
+	for (current = hunk->start; current < hunk->end; ) {
+		for (eol = current; eol < hunk->end; eol++)
+			if (plain[eol] == '\n')
+				break;
+		next = eol + (eol < hunk->end);
+		if (eol > current && plain[eol - 1] == '\r')
+			eol--;
+
+		strbuf_addstr(&s->colored,
+			      plain[current] == '-' ?
+			      s->s.file_old_color :
+			      plain[current] == '+' ?
+			      s->s.file_new_color :
+			      s->s.context_color);
+		strbuf_add(&s->colored, plain + current, eol - current);
+		strbuf_addstr(&s->colored, GIT_COLOR_RESET);
+		if (next > eol)
+			strbuf_add(&s->colored, plain + eol, next - eol);
+		current = next;
+	}
+	hunk->colored_end = s->colored.len;
+}
+
+static int edit_hunk_manually(struct add_p_state *s, struct hunk *hunk)
+{
+	size_t i;
+
+	strbuf_reset(&s->buf);
+	strbuf_commented_addf(&s->buf, _("Manual hunk edit mode -- see bottom for "
+				      "a quick guide.\n"));
+	render_hunk(s, hunk, 0, 0, &s->buf);
+	strbuf_commented_addf(&s->buf,
+			      _("---\n"
+				"To remove '%c' lines, make them ' ' lines "
+				"(context).\n"
+				"To remove '%c' lines, delete them.\n"
+				"Lines starting with %c will be removed.\n"),
+			      s->mode->is_reverse ? '+' : '-',
+			      s->mode->is_reverse ? '-' : '+',
+			      comment_line_char);
+	strbuf_commented_addf(&s->buf, "%s", _(s->mode->edit_hunk_hint));
+	/*
+	 * TRANSLATORS: 'it' refers to the patch mentioned in the previous
+	 * messages.
+	 */
+	strbuf_commented_addf(&s->buf,
+			      _("If it does not apply cleanly, you will be "
+				"given an opportunity to\n"
+				"edit again.  If all lines of the hunk are "
+				"removed, then the edit is\n"
+				"aborted and the hunk is left unchanged.\n"));
+
+	if (strbuf_edit_interactively(&s->buf, "addp-hunk-edit.diff", NULL) < 0)
+		return -1;
+
+	/* strip out commented lines */
+	hunk->start = s->plain.len;
+	for (i = 0; i < s->buf.len; ) {
+		size_t next = find_next_line(&s->buf, i);
+
+		if (s->buf.buf[i] != comment_line_char)
+			strbuf_add(&s->plain, s->buf.buf + i, next - i);
+		i = next;
+	}
+
+	hunk->end = s->plain.len;
+	if (hunk->end == hunk->start)
+		/* The user aborted editing by deleting everything */
+		return 0;
+
+	recolor_hunk(s, hunk);
+
+	/*
+	 * If the hunk header is intact, parse it, otherwise simply use the
+	 * hunk header prior to editing (which will adjust `hunk->start` to
+	 * skip the hunk header).
+	 */
+	if (s->plain.buf[hunk->start] == '@' &&
+	    parse_hunk_header(s, hunk) < 0)
+		return error(_("could not parse hunk header"));
+
+	return 1;
+}
+
+static ssize_t recount_edited_hunk(struct add_p_state *s, struct hunk *hunk,
+				   size_t orig_old_count, size_t orig_new_count)
+{
+	struct hunk_header *header = &hunk->header;
+	size_t i;
+
+	header->old_count = header->new_count = 0;
+	for (i = hunk->start; i < hunk->end; ) {
+		switch (s->plain.buf[i]) {
+		case '-':
+			header->old_count++;
+			break;
+		case '+':
+			header->new_count++;
+			break;
+		case ' ': case '\r': case '\n':
+			header->old_count++;
+			header->new_count++;
+			break;
+		}
+
+		i = find_next_line(&s->plain, i);
+	}
+
+	return orig_old_count - orig_new_count
+		- header->old_count + header->new_count;
+}
+
+static int run_apply_check(struct add_p_state *s,
+			   struct file_diff *file_diff)
+{
+	struct child_process cp = CHILD_PROCESS_INIT;
+
+	strbuf_reset(&s->buf);
+	reassemble_patch(s, file_diff, 1, &s->buf);
+
+	setup_child_process(s, &cp,
+			    "apply", "--check", NULL);
+	argv_array_pushv(&cp.args, s->mode->apply_check_args);
+	if (pipe_command(&cp, s->buf.buf, s->buf.len, NULL, 0, NULL, 0))
+		return error(_("'git apply --cached' failed"));
+
+	return 0;
+}
+
+static int read_single_character(struct add_p_state *s)
+{
+	if (s->s.use_single_key) {
+		int res = read_key_without_echo(&s->answer);
+		printf("%s\n", res == EOF ? "" : s->answer.buf);
+		return res;
+	}
+
+	if (strbuf_getline(&s->answer, stdin) == EOF)
+		return EOF;
+	strbuf_trim_trailing_newline(&s->answer);
+	return 0;
+}
+
+static int prompt_yesno(struct add_p_state *s, const char *prompt)
+{
+	for (;;) {
+		color_fprintf(stdout, s->s.prompt_color, "%s", _(prompt));
+		fflush(stdout);
+		if (read_single_character(s) == EOF)
+			return -1;
+		switch (tolower(s->answer.buf[0])) {
+		case 'n': return 0;
+		case 'y': return 1;
+		}
+	}
+}
+
+static int edit_hunk_loop(struct add_p_state *s,
+			  struct file_diff *file_diff, struct hunk *hunk)
+{
+	size_t plain_len = s->plain.len, colored_len = s->colored.len;
+	struct hunk backup;
+
+	backup = *hunk;
+
+	for (;;) {
+		int res = edit_hunk_manually(s, hunk);
+		if (res == 0) {
+			/* abandonded */
+			*hunk = backup;
+			return -1;
+		}
+
+		if (res > 0) {
+			hunk->delta +=
+				recount_edited_hunk(s, hunk,
+						    backup.header.old_count,
+						    backup.header.new_count);
+			if (!run_apply_check(s, file_diff))
+				return 0;
+		}
+
+		/* Drop edits (they were appended to s->plain) */
+		strbuf_setlen(&s->plain, plain_len);
+		strbuf_setlen(&s->colored, colored_len);
+		*hunk = backup;
+
+		/*
+		 * TRANSLATORS: do not translate [y/n]
+		 * The program will only accept that input at this point.
+		 * Consider translating (saying "no" discards!) as
+		 * (saying "n" for "no" discards!) if the translation
+		 * of the word "no" does not start with n.
+		 */
+		res = prompt_yesno(s, _("Your edited hunk does not apply. "
+					"Edit again (saying \"no\" discards!) "
+					"[y/n]? "));
+		if (res < 1)
+			return -1;
+	}
+}
+
+static int apply_for_checkout(struct add_p_state *s, struct strbuf *diff,
+			      int is_reverse)
+{
+	const char *reverse = is_reverse ? "-R" : NULL;
+	struct child_process check_index = CHILD_PROCESS_INIT;
+	struct child_process check_worktree = CHILD_PROCESS_INIT;
+	struct child_process apply_index = CHILD_PROCESS_INIT;
+	struct child_process apply_worktree = CHILD_PROCESS_INIT;
+	int applies_index, applies_worktree;
+
+	setup_child_process(s, &check_index,
+			    "apply", "--cached", "--check", reverse, NULL);
+	applies_index = !pipe_command(&check_index, diff->buf, diff->len,
+				      NULL, 0, NULL, 0);
+
+	setup_child_process(s, &check_worktree,
+			    "apply", "--check", reverse, NULL);
+	applies_worktree = !pipe_command(&check_worktree, diff->buf, diff->len,
+					 NULL, 0, NULL, 0);
+
+	if (applies_worktree && applies_index) {
+		setup_child_process(s, &apply_index,
+				    "apply", "--cached", reverse, NULL);
+		pipe_command(&apply_index, diff->buf, diff->len,
+			     NULL, 0, NULL, 0);
+
+		setup_child_process(s, &apply_worktree,
+				    "apply", reverse, NULL);
+		pipe_command(&apply_worktree, diff->buf, diff->len,
+			     NULL, 0, NULL, 0);
+
+		return 1;
+	}
+
+	if (!applies_index) {
+		err(s, _("The selected hunks do not apply to the index!"));
+		if (prompt_yesno(s, _("Apply them to the worktree "
+					  "anyway? ")) > 0) {
+			setup_child_process(s, &apply_worktree,
+					    "apply", reverse, NULL);
+			return pipe_command(&apply_worktree, diff->buf,
+					    diff->len, NULL, 0, NULL, 0);
+		}
+		err(s, _("Nothing was applied.\n"));
+	} else
+		/* As a last resort, show the diff to the user */
+		fwrite(diff->buf, diff->len, 1, stderr);
+
+	return 0;
+}
+
+#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_remainder[] =
+N_("j - leave this hunk undecided, see next undecided 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"
+   "/ - search for a hunk matching the given regex\n"
+   "s - split the current hunk into smaller hunks\n"
+   "e - manually edit the current hunk\n"
+   "? - print help\n");
+
+static int patch_update_file(struct add_p_state *s,
+			     struct file_diff *file_diff)
+{
+	size_t hunk_index = 0;
+	ssize_t i, undecided_previous, undecided_next;
+	struct hunk *hunk;
+	char ch;
+	struct child_process cp = CHILD_PROCESS_INIT;
+	int colored = !!s->colored.len, quit = 0;
+	enum prompt_mode_type prompt_mode_type;
+
+	if (!file_diff->hunk_nr)
+		return 0;
+
+	strbuf_reset(&s->buf);
+	render_diff_header(s, file_diff, colored, &s->buf);
+	fputs(s->buf.buf, stdout);
+	for (;;) {
+		if (hunk_index >= file_diff->hunk_nr)
+			hunk_index = 0;
+		hunk = file_diff->hunk + hunk_index;
+
+		undecided_previous = -1;
+		for (i = hunk_index - 1; i >= 0; i--)
+			if (file_diff->hunk[i].use == UNDECIDED_HUNK) {
+				undecided_previous = i;
+				break;
+			}
+
+		undecided_next = -1;
+		for (i = hunk_index + 1; i < file_diff->hunk_nr; i++)
+			if (file_diff->hunk[i].use == UNDECIDED_HUNK) {
+				undecided_next = i;
+				break;
+			}
+
+		/* Everything decided? */
+		if (undecided_previous < 0 && undecided_next < 0 &&
+		    hunk->use != UNDECIDED_HUNK)
+			break;
+
+		strbuf_reset(&s->buf);
+		render_hunk(s, hunk, 0, colored, &s->buf);
+		fputs(s->buf.buf, stdout);
+
+		strbuf_reset(&s->buf);
+		if (undecided_previous >= 0)
+			strbuf_addstr(&s->buf, ",k");
+		if (hunk_index)
+			strbuf_addstr(&s->buf, ",K");
+		if (undecided_next >= 0)
+			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 &&
+		    !file_diff->deleted)
+			strbuf_addstr(&s->buf, ",e");
+
+		if (file_diff->deleted)
+			prompt_mode_type = PROMPT_DELETION;
+		else if (file_diff->mode_change && !hunk_index)
+			prompt_mode_type = PROMPT_MODE_CHANGE;
+		else
+			prompt_mode_type = PROMPT_HUNK;
+
+		color_fprintf(stdout, s->s.prompt_color,
+			      "(%"PRIuMAX"/%"PRIuMAX") ",
+			      (uintmax_t)hunk_index + 1,
+			      (uintmax_t)file_diff->hunk_nr);
+		color_fprintf(stdout, s->s.prompt_color,
+			      _(s->mode->prompt_mode[prompt_mode_type]),
+			      s->buf.buf);
+		fflush(stdout);
+		if (read_single_character(s) == EOF)
+			break;
+
+		if (!s->answer.len)
+			continue;
+		ch = tolower(s->answer.buf[0]);
+		if (ch == 'y') {
+			hunk->use = USE_HUNK;
+soft_increment:
+			hunk_index = undecided_next < 0 ?
+				file_diff->hunk_nr : undecided_next;
+		} else if (ch == 'n') {
+			hunk->use = SKIP_HUNK;
+			goto soft_increment;
+		} else if (ch == 'a') {
+			for (; hunk_index < file_diff->hunk_nr; hunk_index++) {
+				hunk = file_diff->hunk + hunk_index;
+				if (hunk->use == UNDECIDED_HUNK)
+					hunk->use = USE_HUNK;
+			}
+		} else if (ch == 'd' || ch == 'q') {
+			for (; hunk_index < file_diff->hunk_nr; hunk_index++) {
+				hunk = file_diff->hunk + hunk_index;
+				if (hunk->use == UNDECIDED_HUNK)
+					hunk->use = SKIP_HUNK;
+			}
+			if (ch == 'q') {
+				quit = 1;
+				break;
+			}
+		} else if (s->answer.buf[0] == 'K') {
+			if (hunk_index)
+				hunk_index--;
+			else
+				err(s, _("No previous hunk"));
+		} else if (s->answer.buf[0] == 'J') {
+			if (hunk_index + 1 < file_diff->hunk_nr)
+				hunk_index++;
+			else
+				err(s, _("No next hunk"));
+		} else if (s->answer.buf[0] == 'k') {
+			if (undecided_previous >= 0)
+				hunk_index = undecided_previous;
+			else
+				err(s, _("No previous hunk"));
+		} else if (s->answer.buf[0] == 'j') {
+			if (undecided_next >= 0)
+				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] == '/') {
+			regex_t regex;
+			int ret;
+
+			if (file_diff->hunk_nr < 2) {
+				err(s, _("No other hunks to search"));
+				continue;
+			}
+			strbuf_remove(&s->answer, 0, 1);
+			strbuf_trim_trailing_newline(&s->answer);
+			if (s->answer.len == 0) {
+				printf("%s", _("search for regex? "));
+				fflush(stdout);
+				if (strbuf_getline(&s->answer,
+						   stdin) == EOF)
+					break;
+				strbuf_trim_trailing_newline(&s->answer);
+				if (s->answer.len == 0)
+					continue;
+			}
+			ret = regcomp(&regex, s->answer.buf,
+				      REG_EXTENDED | REG_NOSUB | REG_NEWLINE);
+			if (ret) {
+				char errbuf[1024];
+
+				regerror(ret, &regex, errbuf, sizeof(errbuf));
+				err(s, _("Malformed search regexp %s: %s"),
+				    s->answer.buf, errbuf);
+				continue;
+			}
+			i = hunk_index;
+			for (;;) {
+				/* render the hunk into a scratch buffer */
+				render_hunk(s, file_diff->hunk + i, 0, 0,
+					    &s->buf);
+				if (regexec(&regex, s->buf.buf, 0, NULL, 0)
+				    != REG_NOMATCH)
+					break;
+				i++;
+				if (i == file_diff->hunk_nr)
+					i = 0;
+				if (i != hunk_index)
+					continue;
+				err(s, _("No hunk matches the given pattern"));
+				break;
+			}
+			hunk_index = i;
+		} else if (s->answer.buf[0] == 's') {
+			size_t splittable_into = hunk->splittable_into;
+			if (splittable_into < 2)
+				err(s, _("Sorry, cannot split this hunk"));
+			else if (!split_hunk(s, file_diff,
+					     hunk - file_diff->hunk))
+				color_fprintf_ln(stdout, s->s.header_color,
+						 _("Split into %d hunks."),
+						 (int)splittable_into);
+		} else if (s->answer.buf[0] == 'e') {
+			if (hunk_index + 1 == file_diff->mode_change)
+				err(s, _("Sorry, cannot edit this hunk"));
+			else if (edit_hunk_loop(s, file_diff, hunk) >= 0) {
+				hunk->use = USE_HUNK;
+				goto soft_increment;
+			}
+		} else {
+			const char *p = _(help_patch_remainder), *eol = p;
+
+			color_fprintf(stdout, s->s.help_color, "%s",
+				      _(s->mode->help_patch_text));
+
+			/*
+			 * Show only those lines of the remainder that are
+			 * actually applicable with the current hunk.
+			 */
+			for (; *p; p = eol + (*eol == '\n')) {
+				eol = strchrnul(p, '\n');
+
+				/*
+				 * `s->buf` still contains the part of the
+				 * commands shown in the prompt that are not
+				 * always available.
+				 */
+				if (*p != '?' && !strchr(s->buf.buf, *p))
+					continue;
+
+				color_fprintf_ln(stdout, s->s.help_color,
+						 "%.*s", (int)(eol - p), p);
+			}
+		}
+	}
+
+	/* Any hunk to be used? */
+	for (i = 0; i < file_diff->hunk_nr; i++)
+		if (file_diff->hunk[i].use == USE_HUNK)
+			break;
+
+	if (i < file_diff->hunk_nr) {
+		/* At least one hunk selected: apply */
+		strbuf_reset(&s->buf);
+		reassemble_patch(s, file_diff, 0, &s->buf);
+
+		discard_index(s->s.r->index);
+		if (s->mode->apply_for_checkout)
+			apply_for_checkout(s, &s->buf,
+					   s->mode->is_reverse);
+		else {
+			setup_child_process(s, &cp, "apply", NULL);
+			argv_array_pushv(&cp.args, s->mode->apply_args);
+			if (pipe_command(&cp, s->buf.buf, s->buf.len,
+					 NULL, 0, NULL, 0))
+				error(_("'git apply' failed"));
+		}
+		if (!repo_read_index(s->s.r))
+			repo_refresh_and_write_index(s->s.r, REFRESH_QUIET, 0,
+						     1, NULL, NULL, NULL);
+	}
+
+	putchar('\n');
+	return quit;
+}
+
+int run_add_p(struct repository *r, enum add_p_mode mode,
+	      const char *revision, const struct pathspec *ps)
+{
+	struct add_p_state s = {
+		{ r }, STRBUF_INIT, STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
+	};
+	size_t i, binary_count = 0;
+
+	init_add_i_state(&s.s, r);
+
+	if (mode == ADD_P_STASH)
+		s.mode = &patch_mode_stash;
+	else if (mode == ADD_P_RESET) {
+		if (!revision || !strcmp(revision, "HEAD"))
+			s.mode = &patch_mode_reset_head;
+		else
+			s.mode = &patch_mode_reset_nothead;
+	} else if (mode == ADD_P_CHECKOUT) {
+		if (!revision)
+			s.mode = &patch_mode_checkout_index;
+		else if (!strcmp(revision, "HEAD"))
+			s.mode = &patch_mode_checkout_head;
+		else
+			s.mode = &patch_mode_checkout_nothead;
+	} else if (mode == ADD_P_WORKTREE) {
+		if (!revision)
+			s.mode = &patch_mode_checkout_index;
+		else if (!strcmp(revision, "HEAD"))
+			s.mode = &patch_mode_worktree_head;
+		else
+			s.mode = &patch_mode_worktree_nothead;
+	} else
+		s.mode = &patch_mode_add;
+	s.revision = revision;
+
+	if (discard_index(r->index) < 0 || repo_read_index(r) < 0 ||
+	    (!s.mode->index_only &&
+	     repo_refresh_and_write_index(r, REFRESH_QUIET, 0, 1,
+					  NULL, NULL, NULL) < 0) ||
+	    parse_diff(&s, ps) < 0) {
+		strbuf_release(&s.plain);
+		strbuf_release(&s.colored);
+		clear_add_i_state(&s.s);
+		return -1;
+	}
+
+	for (i = 0; i < s.file_diff_nr; i++)
+		if (s.file_diff[i].binary && !s.file_diff[i].hunk_nr)
+			binary_count++;
+		else if (patch_update_file(&s, s.file_diff + i))
+			break;
+
+	if (s.file_diff_nr == 0)
+		fprintf(stderr, _("No changes.\n"));
+	else if (binary_count == s.file_diff_nr)
+		fprintf(stderr, _("Only binary files changed.\n"));
+
+	strbuf_release(&s.answer);
+	strbuf_release(&s.buf);
+	strbuf_release(&s.plain);
+	strbuf_release(&s.colored);
+	clear_add_i_state(&s.s);
+	return 0;
+}