From 1e02bf2d63e99a6416238999b646998af960bc4b Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Mon, 25 Nov 2019 16:13:45 +0100
Subject: [PATCH 1/9] add-interactive: make sure to release `rev.prune_data`

During a review, Junio Hamano pointed out that the `rev.prune_data` was
copied from another pathspec but never cleaned up.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 add-interactive.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/add-interactive.c b/add-interactive.c
index d6cb98cd405fc4..de2fccb0ef3382 100644
--- a/add-interactive.c
+++ b/add-interactive.c
@@ -435,6 +435,9 @@ static int get_modified_files(struct repository *r, struct string_list *files,
 			rev.diffopt.flags.ignore_dirty_submodules = 1;
 			run_diff_files(&rev, 0);
 		}
+
+		if (ps)
+			clear_pathspec(&rev.prune_data);
 	}
 	hashmap_free_entries(&s.file_map, struct pathname_entry, ent);
 

From fab098d86eb47d8ef108e62080db87c1381b2e56 Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Tue, 5 Mar 2019 23:33:55 +0100
Subject: [PATCH 2/9] built-in add -i: allow filtering the modified files list

In the `update` command of `git add -i`, we are primarily interested in the
list of modified files that have worktree (i.e. unstaged) changes.

At the same time, we need to determine _also_ the staged changes, to be
able to produce the full added/deleted information.

The Perl script version of `git add -i` has a parameter of the
`list_modified()` function for that matter. In C, we can be a lot more
precise, using an `enum`.

The C implementation of the filter also has an easier time to avoid
unnecessary work, simply by using an adaptive order of the `diff-index`
and `diff-files` phases, and then skipping files in the second phase
when they have not been seen in the first phase.

Seeing as we change the meaning of the `phase` field, we rename it to
`mode` to reflect that the order depends on the exact invocation of the
`git add -i` command.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 add-interactive.c | 33 ++++++++++++++++++++++++++-------
 1 file changed, 26 insertions(+), 7 deletions(-)

diff --git a/add-interactive.c b/add-interactive.c
index de2fccb0ef3382..c62d63e35b85ce 100644
--- a/add-interactive.c
+++ b/add-interactive.c
@@ -344,10 +344,11 @@ static int pathname_entry_cmp(const void *unused_cmp_data,
 }
 
 struct collection_status {
-	enum { FROM_WORKTREE = 0, FROM_INDEX = 1 } phase;
+	enum { FROM_WORKTREE = 0, FROM_INDEX = 1 } mode;
 
 	const char *reference;
 
+	unsigned skip_unseen:1;
 	struct string_list *files;
 	struct hashmap file_map;
 };
@@ -375,6 +376,9 @@ static void collect_changes_cb(struct diff_queue_struct *q,
 		entry = hashmap_get_entry_from_hash(&s->file_map, hash, name,
 						    struct pathname_entry, ent);
 		if (!entry) {
+			if (s->skip_unseen)
+				continue;
+
 			add_file_item(s->files, name);
 
 			entry = xcalloc(sizeof(*entry), 1);
@@ -385,7 +389,7 @@ static void collect_changes_cb(struct diff_queue_struct *q,
 		}
 
 		file_item = entry->item;
-		adddel = s->phase == FROM_INDEX ?
+		adddel = s->mode == FROM_INDEX ?
 			&file_item->index : &file_item->worktree;
 		adddel->seen = 1;
 		adddel->add = stat.files[i]->added;
@@ -396,13 +400,22 @@ static void collect_changes_cb(struct diff_queue_struct *q,
 	free_diffstat_info(&stat);
 }
 
-static int get_modified_files(struct repository *r, struct string_list *files,
+enum modified_files_filter {
+	NO_FILTER = 0,
+	WORKTREE_ONLY = 1,
+	INDEX_ONLY = 2,
+};
+
+static int get_modified_files(struct repository *r,
+			      enum modified_files_filter filter,
+			      struct string_list *files,
 			      const struct pathspec *ps)
 {
 	struct object_id head_oid;
 	int is_initial = !resolve_ref_unsafe("HEAD", RESOLVE_REF_READING,
 					     &head_oid, NULL);
-	struct collection_status s = { FROM_WORKTREE };
+	struct collection_status s = { 0 };
+	int i;
 
 	if (discard_index(r->index) < 0 ||
 	    repo_read_index_preload(r, ps, 0) < 0)
@@ -412,10 +425,16 @@ static int get_modified_files(struct repository *r, struct string_list *files,
 	s.files = files;
 	hashmap_init(&s.file_map, pathname_entry_cmp, NULL, 0);
 
-	for (s.phase = FROM_WORKTREE; s.phase <= FROM_INDEX; s.phase++) {
+	for (i = 0; i < 2; i++) {
 		struct rev_info rev;
 		struct setup_revision_opt opt = { 0 };
 
+		if (filter == INDEX_ONLY)
+			s.mode = (i == 0) ? FROM_INDEX : FROM_WORKTREE;
+		else
+			s.mode = (i == 0) ? FROM_WORKTREE : FROM_INDEX;
+		s.skip_unseen = filter && i;
+
 		opt.def = is_initial ?
 			empty_tree_oid_hex() : oid_to_hex(&head_oid);
 
@@ -429,7 +448,7 @@ static int get_modified_files(struct repository *r, struct string_list *files,
 		if (ps)
 			copy_pathspec(&rev.prune_data, ps);
 
-		if (s.phase == FROM_INDEX)
+		if (s.mode == FROM_INDEX)
 			run_diff_index(&rev, 1);
 		else {
 			rev.diffopt.flags.ignore_dirty_submodules = 1;
@@ -502,7 +521,7 @@ static void print_file_item(int i, struct string_list_item *item,
 static int run_status(struct add_i_state *s, const struct pathspec *ps,
 		      struct string_list *files, struct list_options *opts)
 {
-	if (get_modified_files(s->r, files, ps) < 0)
+	if (get_modified_files(s->r, NO_FILTER, files, ps) < 0)
 		return -1;
 
 	list(s, files, opts);

From 58a581f4ee020f3557bbca889355ba54b7399b56 Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Thu, 7 Mar 2019 21:36:11 +0100
Subject: [PATCH 3/9] built-in add -i: prepare for multi-selection commands

The `update`, `revert` and `add-untracked` commands allow selecting
multiple entries. Let's extend the `list_and_choose()` function to
accommodate those use cases.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 add-interactive.c | 114 ++++++++++++++++++++++++++++++++++++----------
 1 file changed, 89 insertions(+), 25 deletions(-)

diff --git a/add-interactive.c b/add-interactive.c
index c62d63e35b85ce..ea406e903b7993 100644
--- a/add-interactive.c
+++ b/add-interactive.c
@@ -72,15 +72,17 @@ static void init_add_i_state(struct add_i_state *s, struct repository *r)
 struct prefix_item_list {
 	struct string_list items;
 	struct string_list sorted;
+	int *selected; /* for multi-selections */
 	size_t min_length, max_length;
 };
 #define PREFIX_ITEM_LIST_INIT \
-	{ STRING_LIST_INIT_DUP, STRING_LIST_INIT_NODUP, 1, 4 }
+	{ STRING_LIST_INIT_DUP, STRING_LIST_INIT_NODUP, NULL, 1, 4 }
 
 static void prefix_item_list_clear(struct prefix_item_list *list)
 {
 	string_list_clear(&list->items, 1);
 	string_list_clear(&list->sorted, 0);
+	FREE_AND_NULL(list->selected);
 }
 
 static void extend_prefix_length(struct string_list_item *p,
@@ -182,11 +184,12 @@ static ssize_t find_unique(const char *string, struct prefix_item_list *list)
 struct list_options {
 	int columns;
 	const char *header;
-	void (*print_item)(int i, struct string_list_item *item, void *print_item_data);
+	void (*print_item)(int i, int selected, struct string_list_item *item,
+			   void *print_item_data);
 	void *print_item_data;
 };
 
-static void list(struct add_i_state *s, struct string_list *list,
+static void list(struct add_i_state *s, struct string_list *list, int *selected,
 		 struct list_options *opts)
 {
 	int i, last_lf = 0;
@@ -199,7 +202,8 @@ static void list(struct add_i_state *s, struct string_list *list,
 				 "%s", opts->header);
 
 	for (i = 0; i < list->nr; i++) {
-		opts->print_item(i, list->items + i, opts->print_item_data);
+		opts->print_item(i, selected ? selected[i] : 0, list->items + i,
+				 opts->print_item_data);
 
 		if ((opts->columns) && ((i + 1) % (opts->columns))) {
 			putchar('\t');
@@ -218,6 +222,10 @@ struct list_and_choose_options {
 	struct list_options list_opts;
 
 	const char *prompt;
+	enum {
+		SINGLETON = (1<<0),
+		IMMEDIATE = (1<<1),
+	} flags;
 	void (*print_help)(struct add_i_state *s);
 };
 
@@ -225,7 +233,8 @@ struct list_and_choose_options {
 #define LIST_AND_CHOOSE_QUIT  (-2)
 
 /*
- * Returns the selected index.
+ * Returns the selected index in singleton mode, the number of selected items
+ * otherwise.
  *
  * If an error occurred, returns `LIST_AND_CHOOSE_ERROR`. Upon EOF,
  * `LIST_AND_CHOOSE_QUIT` is returned.
@@ -234,8 +243,19 @@ static ssize_t list_and_choose(struct add_i_state *s,
 			       struct prefix_item_list *items,
 			       struct list_and_choose_options *opts)
 {
+	int singleton = opts->flags & SINGLETON;
+	int immediate = opts->flags & IMMEDIATE;
+
 	struct strbuf input = STRBUF_INIT;
-	ssize_t res = LIST_AND_CHOOSE_ERROR;
+	ssize_t res = singleton ? LIST_AND_CHOOSE_ERROR : 0;
+
+	if (!singleton) {
+		free(items->selected);
+		CALLOC_ARRAY(items->selected, items->items.nr);
+	}
+
+	if (singleton && !immediate)
+		BUG("singleton requires immediate");
 
 	find_unique_prefixes(items);
 
@@ -244,15 +264,16 @@ static ssize_t list_and_choose(struct add_i_state *s,
 
 		strbuf_reset(&input);
 
-		list(s, &items->items, &opts->list_opts);
+		list(s, &items->items, items->selected, &opts->list_opts);
 
 		color_fprintf(stdout, s->prompt_color, "%s", opts->prompt);
-		fputs("> ", stdout);
+		fputs(singleton ? "> " : ">> ", stdout);
 		fflush(stdout);
 
 		if (strbuf_getline(&input, stdin) == EOF) {
 			putchar('\n');
-			res = LIST_AND_CHOOSE_QUIT;
+			if (immediate)
+				res = LIST_AND_CHOOSE_QUIT;
 			break;
 		}
 		strbuf_trim(&input);
@@ -268,7 +289,9 @@ static ssize_t list_and_choose(struct add_i_state *s,
 		p = input.buf;
 		for (;;) {
 			size_t sep = strcspn(p, " \t\r\n,");
-			ssize_t index = -1;
+			int choose = 1;
+			/* `from` is inclusive, `to` is exclusive */
+			ssize_t from = -1, to = -1;
 
 			if (!sep) {
 				if (!*p)
@@ -277,30 +300,70 @@ static ssize_t list_and_choose(struct add_i_state *s,
 				continue;
 			}
 
-			if (isdigit(*p)) {
+			/* Input that begins with '-'; de-select */
+			if (*p == '-') {
+				choose = 0;
+				p++;
+				sep--;
+			}
+
+			if (sep == 1 && *p == '*') {
+				from = 0;
+				to = items->items.nr;
+			} else if (isdigit(*p)) {
 				char *endp;
-				index = strtoul(p, &endp, 10) - 1;
-				if (endp != p + sep)
-					index = -1;
+				/*
+				 * A range can be specified like 5-7 or 5-.
+				 *
+				 * Note: `from` is 0-based while the user input
+				 * is 1-based, hence we have to decrement by
+				 * one. We do not have to decrement `to` even
+				 * if it is 0-based because it is an exclusive
+				 * boundary.
+				 */
+				from = strtoul(p, &endp, 10) - 1;
+				if (endp == p + sep)
+					to = from + 1;
+				else if (*endp == '-') {
+					to = strtoul(++endp, &endp, 10);
+					/* extra characters after the range? */
+					if (endp != p + sep)
+						from = -1;
+				}
 			}
 
 			if (p[sep])
 				p[sep++] = '\0';
-			if (index < 0)
-				index = find_unique(p, items);
+			if (from < 0) {
+				from = find_unique(p, items);
+				if (from >= 0)
+					to = from + 1;
+			}
 
-			if (index < 0 || index >= items->items.nr)
+			if (from < 0 || from >= items->items.nr ||
+			    (singleton && from + 1 != to)) {
 				color_fprintf_ln(stdout, s->error_color,
 						 _("Huh (%s)?"), p);
-			else {
-				res = index;
+				break;
+			} else if (singleton) {
+				res = from;
 				break;
 			}
 
+			if (to > items->items.nr)
+				to = items->items.nr;
+
+			for (; from < to; from++)
+				if (items->selected[from] != choose) {
+					items->selected[from] = choose;
+					res += choose ? +1 : -1;
+				}
+
 			p += sep;
 		}
 
-		if (res != LIST_AND_CHOOSE_ERROR)
+		if ((immediate && res != LIST_AND_CHOOSE_ERROR) ||
+		    !strcmp(input.buf, "*"))
 			break;
 	}
 
@@ -500,7 +563,7 @@ struct print_file_item_data {
 	struct strbuf buf, index, worktree;
 };
 
-static void print_file_item(int i, struct string_list_item *item,
+static void print_file_item(int i, int selected, struct string_list_item *item,
 			    void *print_file_item_data)
 {
 	struct file_item *c = item->util;
@@ -515,7 +578,7 @@ static void print_file_item(int i, struct string_list_item *item,
 	strbuf_addf(&d->buf, d->modified_fmt,
 		    d->index.buf, d->worktree.buf, item->string);
 
-	printf(" %2d: %s", i + 1, d->buf.buf);
+	printf("%c%2d: %s", selected ? '*' : ' ', i + 1, d->buf.buf);
 }
 
 static int run_status(struct add_i_state *s, const struct pathspec *ps,
@@ -524,7 +587,7 @@ static int run_status(struct add_i_state *s, const struct pathspec *ps,
 	if (get_modified_files(s->r, NO_FILTER, files, ps) < 0)
 		return -1;
 
-	list(s, files, opts);
+	list(s, files, NULL, opts);
 	putchar('\n');
 
 	return 0;
@@ -563,7 +626,8 @@ struct print_command_item_data {
 	const char *color, *reset;
 };
 
-static void print_command_item(int i, struct string_list_item *item,
+static void print_command_item(int i, int selected,
+			       struct string_list_item *item,
 			       void *print_command_item_data)
 {
 	struct print_command_item_data *d = print_command_item_data;
@@ -596,7 +660,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 	struct print_command_item_data data = { "[", "]" };
 	struct list_and_choose_options main_loop_opts = {
 		{ 4, N_("*** Commands ***"), print_command_item, &data },
-		N_("What now"), command_prompt_help
+		N_("What now"), SINGLETON | IMMEDIATE, command_prompt_help
 	};
 	struct {
 		const char *string;

From c311a29c77f0c05bcb455d387a15ee9c77d765e4 Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Tue, 5 Mar 2019 23:58:49 +0100
Subject: [PATCH 4/9] built-in add -i: implement the `update` command

After `status` and `help`, it is now time to port the `update` command
to C, the second command that is shown in the main loop menu of `git add
-i`.

This `git add -i` command is the first one which lets the user choose a
subset of a list of files, and as such, this patch lays the groundwork
for the other commands of that category:

- It teaches the `print_file_item()` function to show a unique prefix
  if we found any (the code to find it had been added already in the
  previous patch where we colored the unique prefixes of the main loop
  commands, but that patch uses the `print_command_item()` function to
  display the menu items).

- This patch also adds the help text that is shown when the user input
  to select items from the shown list could not be parsed.

- As `get_modified_files()` clears the list of files, it now has to take
  care of clearing the _full_ `prefix_item_list` lest the `sorted` and
  `selected` fields go stale and inconsistent.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 add-interactive.c | 130 +++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 110 insertions(+), 20 deletions(-)

diff --git a/add-interactive.c b/add-interactive.c
index ea406e903b7993..1e34e880696939 100644
--- a/add-interactive.c
+++ b/add-interactive.c
@@ -6,6 +6,7 @@
 #include "revision.h"
 #include "refs.h"
 #include "string-list.h"
+#include "lockfile.h"
 
 struct add_i_state {
 	struct repository *r;
@@ -377,6 +378,7 @@ struct adddel {
 };
 
 struct file_item {
+	size_t prefix_length;
 	struct adddel index, worktree;
 };
 
@@ -471,7 +473,7 @@ enum modified_files_filter {
 
 static int get_modified_files(struct repository *r,
 			      enum modified_files_filter filter,
-			      struct string_list *files,
+			      struct prefix_item_list *files,
 			      const struct pathspec *ps)
 {
 	struct object_id head_oid;
@@ -484,8 +486,8 @@ static int get_modified_files(struct repository *r,
 	    repo_read_index_preload(r, ps, 0) < 0)
 		return error(_("could not read index"));
 
-	string_list_clear(files, 1);
-	s.files = files;
+	prefix_item_list_clear(files);
+	s.files = &files->items;
 	hashmap_init(&s.file_map, pathname_entry_cmp, NULL, 0);
 
 	for (i = 0; i < 2; i++) {
@@ -524,7 +526,7 @@ static int get_modified_files(struct repository *r,
 	hashmap_free_entries(&s.file_map, struct pathname_entry, ent);
 
 	/* While the diffs are ordered already, we ran *two* diffs... */
-	string_list_sort(files);
+	string_list_sort(&files->items);
 
 	return 0;
 }
@@ -559,8 +561,8 @@ static int is_valid_prefix(const char *prefix, size_t prefix_len)
 }
 
 struct print_file_item_data {
-	const char *modified_fmt;
-	struct strbuf buf, index, worktree;
+	const char *modified_fmt, *color, *reset;
+	struct strbuf buf, name, index, worktree;
 };
 
 static void print_file_item(int i, int selected, struct string_list_item *item,
@@ -568,34 +570,96 @@ static void print_file_item(int i, int selected, struct string_list_item *item,
 {
 	struct file_item *c = item->util;
 	struct print_file_item_data *d = print_file_item_data;
+	const char *highlighted = NULL;
 
 	strbuf_reset(&d->index);
 	strbuf_reset(&d->worktree);
 	strbuf_reset(&d->buf);
 
+	/* Format the item with the prefix highlighted. */
+	if (c->prefix_length > 0 &&
+	    is_valid_prefix(item->string, c->prefix_length)) {
+		strbuf_reset(&d->name);
+		strbuf_addf(&d->name, "%s%.*s%s%s", d->color,
+			    (int)c->prefix_length, item->string, d->reset,
+			    item->string + c->prefix_length);
+		highlighted = d->name.buf;
+	}
+
 	render_adddel(&d->worktree, &c->worktree, _("nothing"));
 	render_adddel(&d->index, &c->index, _("unchanged"));
-	strbuf_addf(&d->buf, d->modified_fmt,
-		    d->index.buf, d->worktree.buf, item->string);
+
+	strbuf_addf(&d->buf, d->modified_fmt, d->index.buf, d->worktree.buf,
+		    highlighted ? highlighted : item->string);
 
 	printf("%c%2d: %s", selected ? '*' : ' ', i + 1, d->buf.buf);
 }
 
 static int run_status(struct add_i_state *s, const struct pathspec *ps,
-		      struct string_list *files, struct list_options *opts)
+		      struct prefix_item_list *files,
+		      struct list_and_choose_options *opts)
 {
 	if (get_modified_files(s->r, NO_FILTER, files, ps) < 0)
 		return -1;
 
-	list(s, files, NULL, opts);
+	list(s, &files->items, NULL, &opts->list_opts);
 	putchar('\n');
 
 	return 0;
 }
 
+static int run_update(struct add_i_state *s, const struct pathspec *ps,
+		      struct prefix_item_list *files,
+		      struct list_and_choose_options *opts)
+{
+	int res = 0, fd;
+	size_t count, i;
+	struct lock_file index_lock;
+
+	if (get_modified_files(s->r, WORKTREE_ONLY, files, ps) < 0)
+		return -1;
+
+	if (!files->items.nr) {
+		putchar('\n');
+		return 0;
+	}
+
+	opts->prompt = N_("Update");
+	count = list_and_choose(s, files, opts);
+	if (count <= 0) {
+		putchar('\n');
+		return 0;
+	}
+
+	fd = repo_hold_locked_index(s->r, &index_lock, LOCK_REPORT_ON_ERROR);
+	if (fd < 0) {
+		putchar('\n');
+		return -1;
+	}
+
+	for (i = 0; i < files->items.nr; i++) {
+		const char *name = files->items.items[i].string;
+		if (files->selected[i] &&
+		    add_file_to_index(s->r->index, name, 0) < 0) {
+			res = error(_("could not stage '%s'"), name);
+			break;
+		}
+	}
+
+	if (!res && write_locked_index(s->r->index, &index_lock, COMMIT_LOCK) < 0)
+		res = error(_("could not write index"));
+
+	if (!res)
+		printf(Q_("updated %d path\n",
+			  "updated %d paths\n", count), (int)count);
+
+	putchar('\n');
+	return res;
+}
+
 static int run_help(struct add_i_state *s, const struct pathspec *unused_ps,
-		    struct string_list *unused_files,
-		    struct list_options *unused_opts)
+		    struct prefix_item_list *unused_files,
+		    struct list_and_choose_options *unused_opts)
 {
 	color_fprintf_ln(stdout, s->help_color, "status        - %s",
 			 _("show paths with changes"));
@@ -613,9 +677,29 @@ static int run_help(struct add_i_state *s, const struct pathspec *unused_ps,
 	return 0;
 }
 
+static void choose_prompt_help(struct add_i_state *s)
+{
+	color_fprintf_ln(stdout, s->help_color, "%s",
+			 _("Prompt help:"));
+	color_fprintf_ln(stdout, s->help_color, "1          - %s",
+			 _("select a single item"));
+	color_fprintf_ln(stdout, s->help_color, "3-5        - %s",
+			 _("select a range of items"));
+	color_fprintf_ln(stdout, s->help_color, "2-3,6-9    - %s",
+			 _("select multiple ranges"));
+	color_fprintf_ln(stdout, s->help_color, "foo        - %s",
+			 _("select item based on unique prefix"));
+	color_fprintf_ln(stdout, s->help_color, "-...       - %s",
+			 _("unselect specified items"));
+	color_fprintf_ln(stdout, s->help_color, "*          - %s",
+			 _("choose all items"));
+	color_fprintf_ln(stdout, s->help_color, "           - %s",
+			 _("(empty) finish selecting"));
+}
+
 typedef int (*command_t)(struct add_i_state *s, const struct pathspec *ps,
-			 struct string_list *files,
-			 struct list_options *opts);
+			 struct prefix_item_list *files,
+			 struct list_and_choose_options *opts);
 
 struct command_item {
 	size_t prefix_length;
@@ -667,18 +751,21 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 		command_t command;
 	} command_list[] = {
 		{ "status", run_status },
+		{ "update", run_update },
 		{ "help", run_help },
 	};
 	struct prefix_item_list commands = PREFIX_ITEM_LIST_INIT;
 
 	struct print_file_item_data print_file_item_data = {
-		"%12s %12s %s", STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
+		"%12s %12s %s", NULL, NULL,
+		STRBUF_INIT, STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
 	};
-	struct list_options opts = {
-		0, NULL, print_file_item, &print_file_item_data
+	struct list_and_choose_options opts = {
+		{ 0, NULL, print_file_item, &print_file_item_data },
+		NULL, 0, choose_prompt_help
 	};
 	struct strbuf header = STRBUF_INIT;
-	struct string_list files = STRING_LIST_INIT_DUP;
+	struct prefix_item_list files = PREFIX_ITEM_LIST_INIT;
 	ssize_t i;
 	int res = 0;
 
@@ -699,11 +786,13 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 		data.color = s.prompt_color;
 		data.reset = s.reset_color;
 	}
+	print_file_item_data.color = data.color;
+	print_file_item_data.reset = data.reset;
 
 	strbuf_addstr(&header, "      ");
 	strbuf_addf(&header, print_file_item_data.modified_fmt,
 		    _("staged"), _("unstaged"), _("path"));
-	opts.header = header.buf;
+	opts.list_opts.header = header.buf;
 
 	if (discard_index(r->index) < 0 ||
 	    repo_read_index(r) < 0 ||
@@ -727,8 +816,9 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 		}
 	}
 
-	string_list_clear(&files, 1);
+	prefix_item_list_clear(&files);
 	strbuf_release(&print_file_item_data.buf);
+	strbuf_release(&print_file_item_data.name);
 	strbuf_release(&print_file_item_data.index);
 	strbuf_release(&print_file_item_data.worktree);
 	strbuf_release(&header);

From f70723a160c1ecddf87349fc99af25f7718e1413 Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Wed, 6 Mar 2019 23:06:13 +0100
Subject: [PATCH 5/9] built-in add -i: re-implement `revert` in C

This is a relatively straight-forward port from the Perl version, with
the notable exception that we imitate `git reset -- <paths>` in the C
version rather than the convoluted `git ls-tree HEAD -- <paths> | git
update-index --index-info` followed by `git update-index --force-remove
-- <paths>` for the missed ones.

While at it, we fix the pretty obvious bug where the `revert` command
offers to unstage files that do not have staged changes.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 add-interactive.c | 109 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)

diff --git a/add-interactive.c b/add-interactive.c
index 1e34e880696939..adab17a635cd45 100644
--- a/add-interactive.c
+++ b/add-interactive.c
@@ -657,6 +657,114 @@ static int run_update(struct add_i_state *s, const struct pathspec *ps,
 	return res;
 }
 
+static void revert_from_diff(struct diff_queue_struct *q,
+			     struct diff_options *opt, void *data)
+{
+	int i, add_flags = ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE;
+
+	for (i = 0; i < q->nr; i++) {
+		struct diff_filespec *one = q->queue[i]->one;
+		struct cache_entry *ce;
+
+		if (!(one->mode && !is_null_oid(&one->oid))) {
+			remove_file_from_index(opt->repo->index, one->path);
+			printf(_("note: %s is untracked now.\n"), one->path);
+		} else {
+			ce = make_cache_entry(opt->repo->index, one->mode,
+					      &one->oid, one->path, 0, 0);
+			if (!ce)
+				die(_("make_cache_entry failed for path '%s'"),
+				    one->path);
+			add_index_entry(opt->repo->index, ce, add_flags);
+		}
+	}
+}
+
+static int run_revert(struct add_i_state *s, const struct pathspec *ps,
+		      struct prefix_item_list *files,
+		      struct list_and_choose_options *opts)
+{
+	int res = 0, fd;
+	size_t count, i, j;
+
+	struct object_id oid;
+	int is_initial = !resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, &oid,
+					     NULL);
+	struct lock_file index_lock;
+	const char **paths;
+	struct tree *tree;
+	struct diff_options diffopt = { NULL };
+
+	if (get_modified_files(s->r, INDEX_ONLY, files, ps) < 0)
+		return -1;
+
+	if (!files->items.nr) {
+		putchar('\n');
+		return 0;
+	}
+
+	opts->prompt = N_("Revert");
+	count = list_and_choose(s, files, opts);
+	if (count <= 0)
+		goto finish_revert;
+
+	fd = repo_hold_locked_index(s->r, &index_lock, LOCK_REPORT_ON_ERROR);
+	if (fd < 0) {
+		res = -1;
+		goto finish_revert;
+	}
+
+	if (is_initial)
+		oidcpy(&oid, s->r->hash_algo->empty_tree);
+	else {
+		tree = parse_tree_indirect(&oid);
+		if (!tree) {
+			res = error(_("Could not parse HEAD^{tree}"));
+			goto finish_revert;
+		}
+		oidcpy(&oid, &tree->object.oid);
+	}
+
+	ALLOC_ARRAY(paths, count + 1);
+	for (i = j = 0; i < files->items.nr; i++)
+		if (files->selected[i])
+			paths[j++] = files->items.items[i].string;
+	paths[j] = NULL;
+
+	parse_pathspec(&diffopt.pathspec, 0,
+		       PATHSPEC_PREFER_FULL | PATHSPEC_LITERAL_PATH,
+		       NULL, paths);
+
+	diffopt.output_format = DIFF_FORMAT_CALLBACK;
+	diffopt.format_callback = revert_from_diff;
+	diffopt.flags.override_submodule_config = 1;
+	diffopt.repo = s->r;
+
+	if (do_diff_cache(&oid, &diffopt))
+		res = -1;
+	else {
+		diffcore_std(&diffopt);
+		diff_flush(&diffopt);
+	}
+	free(paths);
+	clear_pathspec(&diffopt.pathspec);
+
+	if (!res && write_locked_index(s->r->index, &index_lock,
+				       COMMIT_LOCK) < 0)
+		res = -1;
+	else
+		res = repo_refresh_and_write_index(s->r, REFRESH_QUIET, 0, 1,
+						   NULL, NULL, NULL);
+
+	if (!res)
+		printf(Q_("reverted %d path\n",
+			  "reverted %d paths\n", count), (int)count);
+
+finish_revert:
+	putchar('\n');
+	return res;
+}
+
 static int run_help(struct add_i_state *s, const struct pathspec *unused_ps,
 		    struct prefix_item_list *unused_files,
 		    struct list_and_choose_options *unused_opts)
@@ -752,6 +860,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 	} command_list[] = {
 		{ "status", run_status },
 		{ "update", run_update },
+		{ "revert", run_revert },
 		{ "help", run_help },
 	};
 	struct prefix_item_list commands = PREFIX_ITEM_LIST_INIT;

From 952fbc8f79760554b3f45ca9a935541a5dbd1a33 Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Thu, 7 Mar 2019 00:59:24 +0100
Subject: [PATCH 6/9] built-in add -i: re-implement `add-untracked` in C

This is yet another command, ported to C. It builds nicely on the
support functions introduced for other commands, with the notable
difference that only names are displayed for untracked files, no
file type or diff summary.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 add-interactive.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)

diff --git a/add-interactive.c b/add-interactive.c
index adab17a635cd45..a719d30b0b1d07 100644
--- a/add-interactive.c
+++ b/add-interactive.c
@@ -7,6 +7,7 @@
 #include "refs.h"
 #include "string-list.h"
 #include "lockfile.h"
+#include "dir.h"
 
 struct add_i_state {
 	struct repository *r;
@@ -563,6 +564,7 @@ static int is_valid_prefix(const char *prefix, size_t prefix_len)
 struct print_file_item_data {
 	const char *modified_fmt, *color, *reset;
 	struct strbuf buf, name, index, worktree;
+	unsigned only_names:1;
 };
 
 static void print_file_item(int i, int selected, struct string_list_item *item,
@@ -586,6 +588,12 @@ static void print_file_item(int i, int selected, struct string_list_item *item,
 		highlighted = d->name.buf;
 	}
 
+	if (d->only_names) {
+		printf("%c%2d: %s", selected ? '*' : ' ', i + 1,
+		       highlighted ? highlighted : item->string);
+		return;
+	}
+
 	render_adddel(&d->worktree, &c->worktree, _("nothing"));
 	render_adddel(&d->index, &c->index, _("unchanged"));
 
@@ -765,6 +773,88 @@ static int run_revert(struct add_i_state *s, const struct pathspec *ps,
 	return res;
 }
 
+static int get_untracked_files(struct repository *r,
+			       struct prefix_item_list *files,
+			       const struct pathspec *ps)
+{
+	struct dir_struct dir = { 0 };
+	size_t i;
+	struct strbuf buf = STRBUF_INIT;
+
+	if (repo_read_index(r) < 0)
+		return error(_("could not read index"));
+
+	prefix_item_list_clear(files);
+	setup_standard_excludes(&dir);
+	add_pattern_list(&dir, EXC_CMDL, "--exclude option");
+	fill_directory(&dir, r->index, ps);
+
+	for (i = 0; i < dir.nr; i++) {
+		struct dir_entry *ent = dir.entries[i];
+
+		if (index_name_is_other(r->index, ent->name, ent->len)) {
+			strbuf_reset(&buf);
+			strbuf_add(&buf, ent->name, ent->len);
+			add_file_item(&files->items, buf.buf);
+		}
+	}
+
+	strbuf_release(&buf);
+	return 0;
+}
+
+static int run_add_untracked(struct add_i_state *s, const struct pathspec *ps,
+		      struct prefix_item_list *files,
+		      struct list_and_choose_options *opts)
+{
+	struct print_file_item_data *d = opts->list_opts.print_item_data;
+	int res = 0, fd;
+	size_t count, i;
+	struct lock_file index_lock;
+
+	if (get_untracked_files(s->r, files, ps) < 0)
+		return -1;
+
+	if (!files->items.nr) {
+		printf(_("No untracked files.\n"));
+		goto finish_add_untracked;
+	}
+
+	opts->prompt = N_("Add untracked");
+	d->only_names = 1;
+	count = list_and_choose(s, files, opts);
+	d->only_names = 0;
+	if (count <= 0)
+		goto finish_add_untracked;
+
+	fd = repo_hold_locked_index(s->r, &index_lock, LOCK_REPORT_ON_ERROR);
+	if (fd < 0) {
+		res = -1;
+		goto finish_add_untracked;
+	}
+
+	for (i = 0; i < files->items.nr; i++) {
+		const char *name = files->items.items[i].string;
+		if (files->selected[i] &&
+		    add_file_to_index(s->r->index, name, 0) < 0) {
+			res = error(_("could not stage '%s'"), name);
+			break;
+		}
+	}
+
+	if (!res &&
+	    write_locked_index(s->r->index, &index_lock, COMMIT_LOCK) < 0)
+		res = error(_("could not write index"));
+
+	if (!res)
+		printf(Q_("added %d path\n",
+			  "added %d paths\n", count), (int)count);
+
+finish_add_untracked:
+	putchar('\n');
+	return res;
+}
+
 static int run_help(struct add_i_state *s, const struct pathspec *unused_ps,
 		    struct prefix_item_list *unused_files,
 		    struct list_and_choose_options *unused_opts)
@@ -861,6 +951,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 		{ "status", run_status },
 		{ "update", run_update },
 		{ "revert", run_revert },
+		{ "add untracked", run_add_untracked },
 		{ "help", run_help },
 	};
 	struct prefix_item_list commands = PREFIX_ITEM_LIST_INIT;

From cbd10da523a0d1f17ad90628b3867fd498dd3675 Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Mon, 11 Mar 2019 10:07:49 +0100
Subject: [PATCH 7/9] built-in add -i: implement the `patch` command

Well, it is not a full implementation yet. In the interest of making
this easy to review (and easy to keep bugs out), we still hand off to
the Perl script to do the actual work.

The `patch` functionality actually makes up for more than half of the
1,800+ lines of `git-add--interactive.perl`. It will be ported from Perl
to C incrementally, later.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 add-interactive.c | 91 +++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 84 insertions(+), 7 deletions(-)

diff --git a/add-interactive.c b/add-interactive.c
index a719d30b0b1d07..cba9688bb5b1a0 100644
--- a/add-interactive.c
+++ b/add-interactive.c
@@ -8,6 +8,7 @@
 #include "string-list.h"
 #include "lockfile.h"
 #include "dir.h"
+#include "run-command.h"
 
 struct add_i_state {
 	struct repository *r;
@@ -375,7 +376,7 @@ static ssize_t list_and_choose(struct add_i_state *s,
 
 struct adddel {
 	uintmax_t add, del;
-	unsigned seen:1, binary:1;
+	unsigned seen:1, unmerged:1, binary:1;
 };
 
 struct file_item {
@@ -415,6 +416,7 @@ struct collection_status {
 	const char *reference;
 
 	unsigned skip_unseen:1;
+	size_t unmerged_count, binary_count;
 	struct string_list *files;
 	struct hashmap file_map;
 };
@@ -437,7 +439,7 @@ static void collect_changes_cb(struct diff_queue_struct *q,
 		int hash = strhash(name);
 		struct pathname_entry *entry;
 		struct file_item *file_item;
-		struct adddel *adddel;
+		struct adddel *adddel, *other_adddel;
 
 		entry = hashmap_get_entry_from_hash(&s->file_map, hash, name,
 						    struct pathname_entry, ent);
@@ -457,11 +459,21 @@ static void collect_changes_cb(struct diff_queue_struct *q,
 		file_item = entry->item;
 		adddel = s->mode == FROM_INDEX ?
 			&file_item->index : &file_item->worktree;
+		other_adddel = s->mode == FROM_INDEX ?
+			&file_item->worktree : &file_item->index;
 		adddel->seen = 1;
 		adddel->add = stat.files[i]->added;
 		adddel->del = stat.files[i]->deleted;
-		if (stat.files[i]->is_binary)
+		if (stat.files[i]->is_binary) {
+			if (!other_adddel->binary)
+				s->binary_count++;
 			adddel->binary = 1;
+		}
+		if (stat.files[i]->is_unmerged) {
+			if (!other_adddel->unmerged)
+				s->unmerged_count++;
+			adddel->unmerged = 1;
+		}
 	}
 	free_diffstat_info(&stat);
 }
@@ -475,7 +487,9 @@ enum modified_files_filter {
 static int get_modified_files(struct repository *r,
 			      enum modified_files_filter filter,
 			      struct prefix_item_list *files,
-			      const struct pathspec *ps)
+			      const struct pathspec *ps,
+			      size_t *unmerged_count,
+			      size_t *binary_count)
 {
 	struct object_id head_oid;
 	int is_initial = !resolve_ref_unsafe("HEAD", RESOLVE_REF_READING,
@@ -525,6 +539,10 @@ static int get_modified_files(struct repository *r,
 			clear_pathspec(&rev.prune_data);
 	}
 	hashmap_free_entries(&s.file_map, struct pathname_entry, ent);
+	if (unmerged_count)
+		*unmerged_count = s.unmerged_count;
+	if (binary_count)
+		*binary_count = s.binary_count;
 
 	/* While the diffs are ordered already, we ran *two* diffs... */
 	string_list_sort(&files->items);
@@ -607,7 +625,7 @@ static int run_status(struct add_i_state *s, const struct pathspec *ps,
 		      struct prefix_item_list *files,
 		      struct list_and_choose_options *opts)
 {
-	if (get_modified_files(s->r, NO_FILTER, files, ps) < 0)
+	if (get_modified_files(s->r, NO_FILTER, files, ps, NULL, NULL) < 0)
 		return -1;
 
 	list(s, &files->items, NULL, &opts->list_opts);
@@ -624,7 +642,7 @@ static int run_update(struct add_i_state *s, const struct pathspec *ps,
 	size_t count, i;
 	struct lock_file index_lock;
 
-	if (get_modified_files(s->r, WORKTREE_ONLY, files, ps) < 0)
+	if (get_modified_files(s->r, WORKTREE_ONLY, files, ps, NULL, NULL) < 0)
 		return -1;
 
 	if (!files->items.nr) {
@@ -703,7 +721,7 @@ static int run_revert(struct add_i_state *s, const struct pathspec *ps,
 	struct tree *tree;
 	struct diff_options diffopt = { NULL };
 
-	if (get_modified_files(s->r, INDEX_ONLY, files, ps) < 0)
+	if (get_modified_files(s->r, INDEX_ONLY, files, ps, NULL, NULL) < 0)
 		return -1;
 
 	if (!files->items.nr) {
@@ -855,6 +873,64 @@ static int run_add_untracked(struct add_i_state *s, const struct pathspec *ps,
 	return res;
 }
 
+static int run_patch(struct add_i_state *s, const struct pathspec *ps,
+		     struct prefix_item_list *files,
+		     struct list_and_choose_options *opts)
+{
+	int res = 0;
+	ssize_t count, i, j;
+	size_t unmerged_count = 0, binary_count = 0;
+
+	if (get_modified_files(s->r, WORKTREE_ONLY, files, ps,
+			       &unmerged_count, &binary_count) < 0)
+		return -1;
+
+	if (unmerged_count || binary_count) {
+		for (i = j = 0; i < files->items.nr; i++) {
+			struct file_item *item = files->items.items[i].util;
+
+			if (item->index.binary || item->worktree.binary) {
+				free(item);
+				free(files->items.items[i].string);
+			} else if (item->index.unmerged ||
+				 item->worktree.unmerged) {
+				color_fprintf_ln(stderr, s->error_color,
+						 _("ignoring unmerged: %s"),
+						 files->items.items[i].string);
+				free(item);
+				free(files->items.items[i].string);
+			} else
+				files->items.items[j++] = files->items.items[i];
+		}
+		files->items.nr = j;
+	}
+
+	if (!files->items.nr) {
+		if (binary_count)
+			fprintf(stderr, _("Only binary files changed.\n"));
+		else
+			fprintf(stderr, _("No changes.\n"));
+		return 0;
+	}
+
+	opts->prompt = N_("Patch update");
+	count = list_and_choose(s, files, opts);
+	if (count >= 0) {
+		struct argv_array args = ARGV_ARRAY_INIT;
+
+		argv_array_pushl(&args, "git", "add--interactive", "--patch",
+				 "--", NULL);
+		for (i = 0; i < files->items.nr; i++)
+			if (files->selected[i])
+				argv_array_push(&args,
+						files->items.items[i].string);
+		res = run_command_v_opt(args.argv, 0);
+		argv_array_clear(&args);
+	}
+
+	return res;
+}
+
 static int run_help(struct add_i_state *s, const struct pathspec *unused_ps,
 		    struct prefix_item_list *unused_files,
 		    struct list_and_choose_options *unused_opts)
@@ -952,6 +1028,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 		{ "update", run_update },
 		{ "revert", run_revert },
 		{ "add untracked", run_add_untracked },
+		{ "patch", run_patch },
 		{ "help", run_help },
 	};
 	struct prefix_item_list commands = PREFIX_ITEM_LIST_INIT;

From e4907112e4b7e053b1436b8bcb8337deb5309463 Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Fri, 8 Mar 2019 15:58:27 +0100
Subject: [PATCH 8/9] built-in add -i: re-implement the `diff` command

It is not only laziness that we simply spawn `git diff -p --cached`
here: this command needs to use the pager, and the pager needs to exit
when the diff is done. Currently we do not have any way to make that
happen if we run the diff in-process. So let's just spawn.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 add-interactive.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/add-interactive.c b/add-interactive.c
index cba9688bb5b1a0..4d7d44a91757ce 100644
--- a/add-interactive.c
+++ b/add-interactive.c
@@ -931,6 +931,47 @@ static int run_patch(struct add_i_state *s, const struct pathspec *ps,
 	return res;
 }
 
+static int run_diff(struct add_i_state *s, const struct pathspec *ps,
+		    struct prefix_item_list *files,
+		    struct list_and_choose_options *opts)
+{
+	int res = 0;
+	ssize_t count, i;
+
+	struct object_id oid;
+	int is_initial = !resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, &oid,
+					     NULL);
+	if (get_modified_files(s->r, INDEX_ONLY, files, ps, NULL, NULL) < 0)
+		return -1;
+
+	if (!files->items.nr) {
+		putchar('\n');
+		return 0;
+	}
+
+	opts->prompt = N_("Review diff");
+	opts->flags = IMMEDIATE;
+	count = list_and_choose(s, files, opts);
+	opts->flags = 0;
+	if (count >= 0) {
+		struct argv_array args = ARGV_ARRAY_INIT;
+
+		argv_array_pushl(&args, "git", "diff", "-p", "--cached",
+				 oid_to_hex(!is_initial ? &oid :
+					    s->r->hash_algo->empty_tree),
+				 "--", NULL);
+		for (i = 0; i < files->items.nr; i++)
+			if (files->selected[i])
+				argv_array_push(&args,
+						files->items.items[i].string);
+		res = run_command_v_opt(args.argv, 0);
+		argv_array_clear(&args);
+	}
+
+	putchar('\n');
+	return res;
+}
+
 static int run_help(struct add_i_state *s, const struct pathspec *unused_ps,
 		    struct prefix_item_list *unused_files,
 		    struct list_and_choose_options *unused_opts)
@@ -1029,6 +1070,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 		{ "revert", run_revert },
 		{ "add untracked", run_add_untracked },
 		{ "patch", run_patch },
+		{ "diff", run_diff },
 		{ "help", run_help },
 	};
 	struct prefix_item_list commands = PREFIX_ITEM_LIST_INIT;

From 5ba6cd31ab5bba6828f4e195ebd17de9c0758ba7 Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Fri, 18 Oct 2019 16:29:10 +0200
Subject: [PATCH 9/9] built-in add -i: offer the `quit` command

We do not really want to `exit()` here, of course, as this is safely
libified code.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 add-interactive.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/add-interactive.c b/add-interactive.c
index 4d7d44a91757ce..f395d54c08df57 100644
--- a/add-interactive.c
+++ b/add-interactive.c
@@ -1071,6 +1071,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 		{ "add untracked", run_add_untracked },
 		{ "patch", run_patch },
 		{ "diff", run_diff },
+		{ "quit", NULL },
 		{ "help", run_help },
 	};
 	struct prefix_item_list commands = PREFIX_ITEM_LIST_INIT;
@@ -1122,17 +1123,22 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 	res = run_status(&s, ps, &files, &opts);
 
 	for (;;) {
+		struct command_item *util;
+
 		i = list_and_choose(&s, &commands, &main_loop_opts);
-		if (i == LIST_AND_CHOOSE_QUIT) {
+		if (i < 0 || i >= commands.items.nr)
+			util = NULL;
+		else
+			util = commands.items.items[i].util;
+
+		if (i == LIST_AND_CHOOSE_QUIT || (util && !util->command)) {
 			printf(_("Bye.\n"));
 			res = 0;
 			break;
 		}
-		if (i != LIST_AND_CHOOSE_ERROR) {
-			struct command_item *util =
-				commands.items.items[i].util;
+
+		if (util)
 			res = util->command(&s, ps, &files, &opts);
-		}
 	}
 
 	prefix_item_list_clear(&files);