git add -i: add a rudimentary version in C (supporting only status and help so far)

new file mode 100644
index 0000000000..540bf185d8
@@ -0,0 +1,13 @@
+#include "cache.h"
+#include "add-interactive.h"
+#include "config.h"
+
+int add_i_config(const char *var, const char *value, void *cb)
+{
+	return git_default_config(var, value, cb);
+}
+
+int run_add_i(struct repository *r, const struct pathspec *ps)
+{
+	die(_("No commands are available in the built-in `git add -i` yet!"));
+}

new file mode 100644
index 0000000000..e6e6e051eb
@@ -0,0 +1,10 @@
+#ifndef ADD_INTERACTIVE_H
+#define ADD_INTERACTIVE_H
+
+int add_i_config(const char *var, const char *value, void *cb);
+
+struct repository;
+struct pathspec;
+int run_add_i(struct repository *r, const struct pathspec *ps);
+
+#endif

index db2dfa4350..5a32a755c8 100644
@@ -20,6 +20,7 @@
 #include "bulk-checkin.h"
 #include "argv-array.h"
 #include "submodule.h"
+#include "add-interactive.h"
 
 static const char * const builtin_add_usage[] = {
 	N_("git add [<options>] [--] <pathspec>..."),

@@ -28,6 +29,7 @@ static const char * const builtin_add_usage[] = {
 static int patch_interactive, add_interactive, edit_interactive;
 static int take_worktree_changes;
 static int add_renormalize;
+static int use_builtin_add_i;
 
 struct update_callback_data {
 	int flags;

@@ -186,6 +188,9 @@ int run_add_interactive(const char *revision, const char *patch_mode,
 	int status, i;
 	struct argv_array argv = ARGV_ARRAY_INIT;
 
+	if (use_builtin_add_i && !patch_mode)
+		return !!run_add_i(the_repository, pathspec);
+
 	argv_array_push(&argv, "add--interactive");
 	if (patch_mode)
 		argv_array_push(&argv, patch_mode);

@@ -319,7 +324,12 @@ static int add_config(const char *var, const char *value, void *cb)
 		ignore_add_errors = git_config_bool(var, value);
 		return 0;
 	}
-	return git_default_config(var, value, cb);
+	if (!strcmp(var, "add.interactive.usebuiltin")) {
+		use_builtin_add_i = git_config_bool(var, value);
+		return 0;
+	}
+
+	return add_i_config(var, value, cb);
 }
 
 static const char embedded_advice[] = N_(

@@ -394,8 +404,12 @@ int cmd_add(int argc, const char **argv, const char *prefix)
 	int require_pathspec;
 	char *seen = NULL;
 	struct lock_file lock_file = LOCK_INIT;
+	int use_builtin_add_i_env =
+		git_env_bool("GIT_TEST_ADD_I_USE_BUILTIN", -1);
 
 	git_config(add_config, NULL);
+	if (use_builtin_add_i_env >= 0)
+		use_builtin_add_i = use_builtin_add_i_env;
 
 	argc = parse_options(argc, argv, prefix, builtin_add_options,
 			  builtin_add_usage, PARSE_OPT_KEEP_ARGV0);

index 5306c48652..daa5f3a736 100644
@@ -2489,22 +2489,6 @@ static void pprint_rename(struct strbuf *name, const char *a, const char *b)
 	}
 }
 
-struct diffstat_t {
-	int nr;
-	int alloc;
-	struct diffstat_file {
-		char *from_name;
-		char *name;
-		char *print_name;
-		const char *comments;
-		unsigned is_unmerged:1;
-		unsigned is_binary:1;
-		unsigned is_renamed:1;
-		unsigned is_interesting:1;
-		uintmax_t added, deleted;
-	} **files;
-};
-
 static struct diffstat_file *diffstat_add(struct diffstat_t *diffstat,
 					  const char *name_a,
 					  const char *name_b)

@@ -6001,12 +5985,7 @@ void diff_flush(struct diff_options *options)
 	    dirstat_by_line) {
 		struct diffstat_t diffstat;
 
-		memset(&diffstat, 0, sizeof(struct diffstat_t));
-		for (i = 0; i < q->nr; i++) {
-			struct diff_filepair *p = q->queue[i];
-			if (check_pair_status(p))
-				diff_flush_stat(p, options, &diffstat);
-		}
+		compute_diffstat(options, &diffstat, q);
 		if (output_format & DIFF_FORMAT_NUMSTAT)
 			show_numstat(&diffstat, options);
 		if (output_format & DIFF_FORMAT_DIFFSTAT)

@@ -6306,6 +6285,20 @@ static int is_submodule_ignored(const char *path, struct diff_options *options)
 	return ignored;
 }
 
+void compute_diffstat(struct diff_options *options,
+		      struct diffstat_t *diffstat,
+		      struct diff_queue_struct *q)
+{
+	int i;
+
+	memset(diffstat, 0, sizeof(struct diffstat_t));
+	for (i = 0; i < q->nr; i++) {
+		struct diff_filepair *p = q->queue[i];
+		if (check_pair_status(p))
+			diff_flush_stat(p, options, diffstat);
+	}
+}
+
 void diff_addremove(struct diff_options *options,
 		    int addremove, unsigned mode,
 		    const struct object_id *oid,

index b512d0477a..ae9bedfab8 100644
@@ -240,6 +240,22 @@ void diff_emit_submodule_error(struct diff_options *o, const char *err);
 void diff_emit_submodule_pipethrough(struct diff_options *o,
 				     const char *line, int len);
 
+struct diffstat_t {
+	int nr;
+	int alloc;
+	struct diffstat_file {
+		char *from_name;
+		char *name;
+		char *print_name;
+		const char *comments;
+		unsigned is_unmerged:1;
+		unsigned is_binary:1;
+		unsigned is_renamed:1;
+		unsigned is_interesting:1;
+		uintmax_t added, deleted;
+	} **files;
+};
+
 enum color_diff {
 	DIFF_RESET = 0,
 	DIFF_CONTEXT = 1,

@@ -328,6 +344,9 @@ void diff_change(struct diff_options *,
 
 struct diff_filepair *diff_unmerge(struct diff_options *, const char *path);
 
+void compute_diffstat(struct diff_options *options, struct diffstat_t *diffstat,
+		      struct diff_queue_struct *q);
+
 #define DIFF_SETUP_REVERSE      	1
 #define DIFF_SETUP_USE_SIZE_CACHE	4
 

index 540bf185d8..f627a56eeb 100644
@@ -1,13 +1,276 @@
 #include "cache.h"
 #include "add-interactive.h"
 #include "config.h"
+#include "diffcore.h"
+#include "revision.h"
+#include "refs.h"
 
 int add_i_config(const char *var, const char *value, void *cb)
 {
 	return git_default_config(var, value, cb);
 }
 
+struct item {
+	const char *name;
+};
+
+struct list_options {
+	const char *header;
+	void (*print_item)(int i, struct item *item, void *print_item_data);
+	void *print_item_data;
+};
+
+static void list(struct item **list, size_t nr, struct list_options *opts)
+{
+	int i;
+
+	if (!nr)
+		return;
+
+	if (opts->header)
+		printf("%s\n", opts->header);
+
+	for (i = 0; i < nr; i++) {
+		opts->print_item(i, list[i], opts->print_item_data);
+		putchar('\n');
+	}
+}
+
+struct adddel {
+	uintmax_t add, del;
+	unsigned seen:1, binary:1;
+};
+
+struct file_list {
+	struct file_item {
+		struct item item;
+		struct adddel index, worktree;
+	} **file;
+	size_t nr, alloc;
+};
+
+static void add_file_item(struct file_list *list, const char *name)
+{
+	struct file_item *item;
+
+	FLEXPTR_ALLOC_STR(item, item.name, name);
+
+	ALLOC_GROW(list->file, list->nr + 1, list->alloc);
+	list->file[list->nr++] = item;
+}
+
+static void reset_file_list(struct file_list *list)
+{
+	size_t i;
+
+	for (i = 0; i < list->nr; i++)
+		free(list->file[i]);
+	list->nr = 0;
+}
+
+static void release_file_list(struct file_list *list)
+{
+	reset_file_list(list);
+	FREE_AND_NULL(list->file);
+	list->alloc = 0;
+}
+
+static int file_item_cmp(const void *a, const void *b)
+{
+	const struct file_item * const *f1 = a;
+	const struct file_item * const *f2 = b;
+
+	return strcmp((*f1)->item.name, (*f2)->item.name);
+}
+
+struct pathname_entry {
+	struct hashmap_entry ent;
+	size_t index;
+	char pathname[FLEX_ARRAY];
+};
+
+static int pathname_entry_cmp(const void *unused_cmp_data,
+			      const void *entry, const void *entry_or_key,
+			      const void *pathname)
+{
+	const struct pathname_entry *e1 = entry, *e2 = entry_or_key;
+
+	return strcmp(e1->pathname,
+		      pathname ? (const char *)pathname : e2->pathname);
+}
+
+struct collection_status {
+	enum { FROM_WORKTREE = 0, FROM_INDEX = 1 } phase;
+
+	const char *reference;
+
+	struct file_list *list;
+	struct hashmap file_map;
+};
+
+static void collect_changes_cb(struct diff_queue_struct *q,
+			       struct diff_options *options,
+			       void *data)
+{
+	struct collection_status *s = data;
+	struct diffstat_t stat = { 0 };
+	int i;
+
+	if (!q->nr)
+		return;
+
+	compute_diffstat(options, &stat, q);
+
+	for (i = 0; i < stat.nr; i++) {
+		const char *name = stat.files[i]->name;
+		int hash = strhash(name);
+		struct pathname_entry *entry;
+		size_t file_index;
+		struct file_item *file;
+		struct adddel *adddel;
+
+		entry = hashmap_get_from_hash(&s->file_map, hash, name);
+		if (entry)
+			file_index = entry->index;
+		else {
+			FLEX_ALLOC_STR(entry, pathname, name);
+			hashmap_entry_init(entry, hash);
+			entry->index = file_index = s->list->nr;
+			hashmap_add(&s->file_map, entry);
+
+			add_file_item(s->list, name);
+		}
+		file = s->list->file[file_index];
+
+		adddel = s->phase == FROM_INDEX ? &file->index : &file->worktree;
+		adddel->seen = 1;
+		adddel->add = stat.files[i]->added;
+		adddel->del = stat.files[i]->deleted;
+		if (stat.files[i]->is_binary)
+			adddel->binary = 1;
+	}
+}
+
+static int get_modified_files(struct repository *r, struct file_list *list,
+			      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 };
+
+	if (repo_read_index_preload(r, ps, 0) < 0)
+		return error(_("could not read index"));
+
+	s.list = list;
+	hashmap_init(&s.file_map, pathname_entry_cmp, NULL, 0);
+
+	for (s.phase = FROM_WORKTREE; s.phase <= FROM_INDEX; s.phase++) {
+		struct rev_info rev;
+		struct setup_revision_opt opt = { 0 };
+
+		opt.def = is_initial ?
+			empty_tree_oid_hex() : oid_to_hex(&head_oid);
+
+		init_revisions(&rev, NULL);
+		setup_revisions(0, NULL, &rev, &opt);
+
+		rev.diffopt.output_format = DIFF_FORMAT_CALLBACK;
+		rev.diffopt.format_callback = collect_changes_cb;
+		rev.diffopt.format_callback_data = &s;
+
+		if (ps)
+			copy_pathspec(&rev.prune_data, ps);
+
+		if (s.phase == FROM_INDEX)
+			run_diff_index(&rev, 1);
+		else {
+			rev.diffopt.flags.ignore_dirty_submodules = 1;
+			run_diff_files(&rev, 0);
+		}
+	}
+	hashmap_free(&s.file_map, 1);
+
+	/* While the diffs are ordered already, we ran *two* diffs... */
+	QSORT(list->file, list->nr, file_item_cmp);
+
+	return 0;
+}
+
+static void populate_wi_changes(struct strbuf *buf,
+				struct adddel *ad, const char *no_changes)
+{
+	if (ad->binary)
+		strbuf_addstr(buf, _("binary"));
+	else if (ad->seen)
+		strbuf_addf(buf, "+%"PRIuMAX"/-%"PRIuMAX,
+			    (uintmax_t)ad->add, (uintmax_t)ad->del);
+	else
+		strbuf_addstr(buf, no_changes);
+}
+
+struct print_file_item_data {
+	const char *modified_fmt;
+	struct strbuf buf, index, worktree;
+};
+
+static void print_file_item(int i, struct item *item,
+			    void *print_file_item_data)
+{
+	struct file_item *c = (struct file_item *)item;
+	struct print_file_item_data *d = print_file_item_data;
+
+	strbuf_reset(&d->index);
+	strbuf_reset(&d->worktree);
+	strbuf_reset(&d->buf);
+
+	populate_wi_changes(&d->worktree, &c->worktree, _("nothing"));
+	populate_wi_changes(&d->index, &c->index, _("unchanged"));
+	strbuf_addf(&d->buf, d->modified_fmt,
+		    d->index.buf, d->worktree.buf, item->name);
+
+	printf(" %2d: %s", i + 1, d->buf.buf);
+}
+
+static int run_status(struct repository *r, const struct pathspec *ps,
+		      struct file_list *files, struct list_options *opts)
+{
+	reset_file_list(files);
+
+	if (get_modified_files(r, files, ps) < 0)
+		return -1;
+
+	if (files->nr)
+		list((struct item **)files->file, files->nr, opts);
+	putchar('\n');
+
+	return 0;
+}
+
 int run_add_i(struct repository *r, const struct pathspec *ps)
 {
-	die(_("No commands are available in the built-in `git add -i` yet!"));
+	struct print_file_item_data print_file_item_data = {
+		"%12s %12s %s", STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
+	};
+	struct list_options opts = {
+		NULL, print_file_item, &print_file_item_data
+	};
+	struct strbuf header = STRBUF_INIT;
+	struct file_list files = { NULL };
+	int res = 0;
+
+	strbuf_addstr(&header, "      ");
+	strbuf_addf(&header, print_file_item_data.modified_fmt,
+		    _("staged"), _("unstaged"), _("path"));
+	opts.header = header.buf;
+
+	res = run_status(r, ps, &files, &opts);
+
+	release_file_list(&files);
+	strbuf_release(&print_file_item_data.buf);
+	strbuf_release(&print_file_item_data.index);
+	strbuf_release(&print_file_item_data.worktree);
+	strbuf_release(&header);
+
+	return res;
 }

index f627a56eeb..d971b58552 100644
@@ -264,7 +264,9 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 		    _("staged"), _("unstaged"), _("path"));
 	opts.header = header.buf;
 
-	res = run_status(r, ps, &files, &opts);
+	repo_refresh_and_write_index(r, REFRESH_QUIET, 1);
+	if (run_status(r, ps, &files, &opts) < 0)
+		res = -1;
 
 	release_file_list(&files);
 	strbuf_release(&print_file_item_data.buf);

index 65e6f8b8fd..c90f310093 100644
@@ -272,3 +272,22 @@ int repo_hold_locked_index(struct repository *repo,
 		BUG("the repo hasn't been setup");
 	return hold_lock_file_for_update(lf, repo->index_file, flags);
 }
+
+int repo_refresh_and_write_index(struct repository *r,
+				 unsigned int flags, int gentle)
+{
+	struct lock_file lock_file = LOCK_INIT;
+	int fd;
+
+	if (repo_read_index_preload(r, NULL, 0) < 0)
+		return error(_("could not read index"));
+	fd = repo_hold_locked_index(r, &lock_file, 0);
+	if (!gentle && fd < 0)
+		return error(_("could not lock index for writing"));
+	refresh_index(r->index, flags, NULL, NULL, NULL);
+	if (0 <= fd)
+		repo_update_index_if_able(r, &lock_file);
+	rollback_lock_file(&lock_file);
+
+	return 0;
+}

index 8981649d43..fb49e0e328 100644
@@ -154,5 +154,12 @@ int repo_read_index_unmerged(struct repository *);
  */
 void repo_update_index_if_able(struct repository *, struct lock_file *);
 
+/*
+ * Refresh the index and write it out. If the index file could not be
+ * locked, error out, except in gentle mode. The flags will be passed
+ * through to refresh_index().
+ */
+int repo_refresh_and_write_index(struct repository *r,
+				 unsigned int flags, int gentle);
 
 #endif /* REPOSITORY_H */

index d971b58552..79adc58321 100644
@@ -1,13 +1,56 @@
 #include "cache.h"
 #include "add-interactive.h"
 #include "config.h"
+#include "color.h"
+#include "config.h"
 #include "diffcore.h"
 #include "revision.h"
 #include "refs.h"
 
+static int use_color = -1;
+
+enum color_add_i {
+	COLOR_HEADER = 0,
+};
+
+static char list_colors[][COLOR_MAXLEN] = {
+	GIT_COLOR_BOLD,      /* Header */
+};
+
+static const char *get_add_i_color(enum color_add_i ix)
+{
+	if (want_color(use_color))
+		return list_colors[ix];
+	return "";
+}
+
+static int parse_color_slot(const char *slot)
+{
+	if (!strcasecmp(slot, "header"))
+		return COLOR_HEADER;
+
+	return -1;
+}
+
 int add_i_config(const char *var, const char *value, void *cb)
 {
-	return git_default_config(var, value, cb);
+	const char *name;
+
+	if (!strcmp(var, "color.interactive")) {
+		use_color = git_config_colorbool(var, value);
+		return 0;
+	}
+
+	if (skip_prefix(var, "color.interactive.", &name)) {
+		int slot = parse_color_slot(name);
+		if (slot < 0)
+			return 0;
+		if (!value)
+			return config_error_nonbool(var);
+		return color_parse(value, list_colors[slot]);
+	}
+
+	return git_color_default_config(var, value, cb);
 }
 
 struct item {

@@ -27,8 +70,10 @@ static void list(struct item **list, size_t nr, struct list_options *opts)
 	if (!nr)
 		return;
 
-	if (opts->header)
-		printf("%s\n", opts->header);
+	if (opts->header) {
+		const char *header_color = get_add_i_color(COLOR_HEADER);
+		color_fprintf_ln(stdout, header_color, "%s", opts->header);
+	}
 
 	for (i = 0; i < nr; i++) {
 		opts->print_item(i, list[i], opts->print_item_data);

index 79adc58321..c8bd62369e 100644
@@ -58,6 +58,7 @@ struct item {
 };
 
 struct list_options {
+	int columns;
 	const char *header;
 	void (*print_item)(int i, struct item *item, void *print_item_data);
 	void *print_item_data;

@@ -65,7 +66,7 @@ struct list_options {
 
 static void list(struct item **list, size_t nr, struct list_options *opts)
 {
-	int i;
+	int i, last_lf = 0;
 
 	if (!nr)
 		return;

@@ -77,8 +78,90 @@ static void list(struct item **list, size_t nr, struct list_options *opts)
 
 	for (i = 0; i < nr; i++) {
 		opts->print_item(i, list[i], opts->print_item_data);
+
+		if ((opts->columns) && ((i + 1) % (opts->columns))) {
+			putchar('\t');
+			last_lf = 0;
+		}
+		else {
+			putchar('\n');
+			last_lf = 1;
+		}
+	}
+
+	if (!last_lf)
 		putchar('\n');
+}
+struct list_and_choose_options {
+	struct list_options list_opts;
+
+	const char *prompt;
+};
+
+/*
+ * Returns the selected index.
+ */
+static ssize_t list_and_choose(struct item **items, size_t nr,
+			       struct list_and_choose_options *opts)
+{
+	struct strbuf input = STRBUF_INIT;
+	ssize_t res = -1;
+
+	for (;;) {
+		char *p, *endp;
+
+		strbuf_reset(&input);
+
+		list(items, nr, &opts->list_opts);
+
+		printf("%s%s", opts->prompt, "> ");
+		fflush(stdout);
+
+		if (strbuf_getline(&input, stdin) == EOF) {
+			putchar('\n');
+			res = -2;
+			break;
+		}
+		strbuf_trim(&input);
+
+		if (!input.len)
+			break;
+
+		p = input.buf;
+		for (;;) {
+			size_t sep = strcspn(p, " \t\r\n,");
+			ssize_t index = -1;
+
+			if (!sep) {
+				if (!*p)
+					break;
+				p++;
+				continue;
+			}
+
+			if (isdigit(*p)) {
+				index = strtoul(p, &endp, 10) - 1;
+				if (endp != p + sep)
+					index = -1;
+			}
+
+			p[sep] = '\0';
+			if (index < 0 || index >= nr)
+				printf(_("Huh (%s)?\n"), p);
+			else {
+				res = index;
+				break;
+			}
+
+			p += sep + 1;
+		}
+
+		if (res >= 0)
+			break;
 	}
+
+	strbuf_release(&input);
+	return res;
 }
 
 struct adddel {

@@ -292,16 +375,39 @@ static int run_status(struct repository *r, const struct pathspec *ps,
 	return 0;
 }
 
+static void print_command_item(int i, struct item *item,
+			       void *print_command_item_data)
+{
+	printf(" %2d: %s", i + 1, item->name);
+}
+
+struct command_item {
+	struct item item;
+	int (*command)(struct repository *r, const struct pathspec *ps,
+		       struct file_list *files, struct list_options *opts);
+};
+
 int run_add_i(struct repository *r, const struct pathspec *ps)
 {
+	struct list_and_choose_options main_loop_opts = {
+		{ 4, N_("*** Commands ***"), print_command_item, NULL },
+		N_("What now")
+	};
+	struct command_item
+		status = { { "status" }, run_status };
+	struct command_item *commands[] = {
+		&status
+	};
+
 	struct print_file_item_data print_file_item_data = {
 		"%12s %12s %s", STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
 	};
 	struct list_options opts = {
-		NULL, print_file_item, &print_file_item_data
+		0, NULL, print_file_item, &print_file_item_data
 	};
 	struct strbuf header = STRBUF_INIT;
 	struct file_list files = { NULL };
+	ssize_t i;
 	int res = 0;
 
 	strbuf_addstr(&header, "      ");

@@ -313,6 +419,18 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 	if (run_status(r, ps, &files, &opts) < 0)
 		res = -1;
 
+	for (;;) {
+		i = list_and_choose((struct item **)commands,
+				    ARRAY_SIZE(commands), &main_loop_opts);
+		if (i < -1) {
+			printf(_("Bye.\n"));
+			res = 0;
+			break;
+		}
+		if (i >= 0)
+			res = commands[i]->command(r, ps, &files, &opts);
+	}
+
 	release_file_list(&files);
 	strbuf_release(&print_file_item_data.buf);
 	strbuf_release(&print_file_item_data.index);

111 lines not on this page · raw message

new file mode 100644
index 0000000000..ce3b8a4a32
@@ -0,0 +1,40 @@
+#ifndef PREFIX_MAP_H
+#define PREFIX_MAP_H
+
+#include "hashmap.h"
+
+struct prefix_item {
+	const char *name;
+	size_t prefix_length;
+};
+
+struct prefix_map_entry {
+	struct hashmap_entry e;
+	const char *name;
+	size_t prefix_length;
+	/* if item is NULL, the prefix is not unique */
+	struct prefix_item *item;
+};
+
+struct prefix_map {
+	struct hashmap map;
+	int min_length, max_length;
+};
+
+/*
+ * Find unique prefixes in a given list of strings.
+ *
+ * Typically, the `struct prefix_item` information will be but a field in the
+ * actual item struct; For this reason, the `list` parameter is specified as a
+ * list of pointers to the items.
+ *
+ * The `min_length`/`max_length` parameters define what length the unique
+ * prefixes should have.
+ *
+ * If no unique prefix could be found for a given item, its `prefix_length`
+ * will be set to 0.
+ */
+void find_unique_prefixes(struct prefix_item **list, size_t nr,
+			  int min_length, int max_length);
+
+#endif

58 lines not on this page · raw message

index 99db7409b8..d6a92a8699 100644
@@ -32,6 +32,7 @@ static struct test_cmd cmds[] = {
 	{ "parse-options", cmd__parse_options },
 	{ "path-utils", cmd__path_utils },
 	{ "pkt-line", cmd__pkt_line },
+	{ "prefix-map", cmd__prefix_map },
 	{ "prio-queue", cmd__prio_queue },
 	{ "reach", cmd__reach },
 	{ "read-cache", cmd__read_cache },

index 25abed1cf2..33a089ee4e 100644
@@ -29,6 +29,7 @@ int cmd__online_cpus(int argc, const char **argv);
 int cmd__parse_options(int argc, const char **argv);
 int cmd__path_utils(int argc, const char **argv);
 int cmd__pkt_line(int argc, const char **argv);
+int cmd__prefix_map(int argc, const char **argv);
 int cmd__prio_queue(int argc, const char **argv);
 int cmd__reach(int argc, const char **argv);
 int cmd__read_cache(int argc, const char **argv);

index c8bd62369e..62ce446dd9 100644
@@ -6,6 +6,7 @@
 #include "diffcore.h"
 #include "revision.h"
 #include "refs.h"
+#include "prefix-map.h"
 
 static int use_color = -1;
 

@@ -53,18 +54,33 @@ int add_i_config(const char *var, const char *value, void *cb)
 	return git_color_default_config(var, value, cb);
 }
 
-struct item {
-	const char *name;
-};
+static ssize_t find_unique(const char *string,
+			   struct prefix_item **list, size_t nr)
+{
+	ssize_t found = -1, i;
+
+	for (i = 0; i < nr; i++) {
+		struct prefix_item *item = list[i];
+		if (!starts_with(item->name, string))
+			continue;
+		if (found >= 0)
+			return -1;
+		found = i;
+	}
+
+	return found;
+}
 
 struct list_options {
 	int columns;
 	const char *header;
-	void (*print_item)(int i, struct item *item, void *print_item_data);
+	void (*print_item)(int i, struct prefix_item *item,
+			   void *print_item_data);
 	void *print_item_data;
 };
 
-static void list(struct item **list, size_t nr, struct list_options *opts)
+static void list(struct prefix_item **list, size_t nr,
+		 struct list_options *opts)
 {
 	int i, last_lf = 0;
 

@@ -101,12 +117,14 @@ struct list_and_choose_options {
 /*
  * Returns the selected index.
  */
-static ssize_t list_and_choose(struct item **items, size_t nr,
+static ssize_t list_and_choose(struct prefix_item **items, size_t nr,
 			       struct list_and_choose_options *opts)
 {
 	struct strbuf input = STRBUF_INIT;
 	ssize_t res = -1;
 
+	find_unique_prefixes(items, nr, 1, 4);
+
 	for (;;) {
 		char *p, *endp;
 

@@ -146,6 +164,9 @@ static ssize_t list_and_choose(struct item **items, size_t nr,
 			}
 
 			p[sep] = '\0';
+			if (index < 0)
+				index = find_unique(p, items, nr);
+
 			if (index < 0 || index >= nr)
 				printf(_("Huh (%s)?\n"), p);
 			else {

@@ -171,7 +192,7 @@ struct adddel {
 
 struct file_list {
 	struct file_item {
-		struct item item;
+		struct prefix_item item;
 		struct adddel index, worktree;
 	} **file;
 	size_t nr, alloc;

@@ -337,12 +358,29 @@ static void populate_wi_changes(struct strbuf *buf,
 		strbuf_addstr(buf, no_changes);
 }
 
+/* filters out prefixes which have special meaning to list_and_choose() */
+static int is_valid_prefix(const char *prefix, size_t prefix_len)
+{
+	return prefix_len && prefix &&
+		/*
+		 * We expect `prefix` to be NUL terminated, therefore this
+		 * `strcspn()` call is okay, even if it might do much more
+		 * work than strictly necessary.
+		 */
+		strcspn(prefix, " \t\r\n,") >= prefix_len &&	/* separators */
+		*prefix != '-' &&				/* deselection */
+		!isdigit(*prefix) &&				/* selection */
+		(prefix_len != 1 ||
+		 (*prefix != '*' &&				/* "all" wildcard */
+		  *prefix != '?'));				/* prompt help */
+}
+
 struct print_file_item_data {
 	const char *modified_fmt;
 	struct strbuf buf, index, worktree;
 };
 
-static void print_file_item(int i, struct item *item,
+static void print_file_item(int i, struct prefix_item *item,
 			    void *print_file_item_data)
 {
 	struct file_item *c = (struct file_item *)item;

@@ -369,20 +407,26 @@ static int run_status(struct repository *r, const struct pathspec *ps,
 		return -1;
 
 	if (files->nr)
-		list((struct item **)files->file, files->nr, opts);
+		list((struct prefix_item **)files->file, files->nr, opts);
 	putchar('\n');
 
 	return 0;
 }
 
-static void print_command_item(int i, struct item *item,
+static void print_command_item(int i, struct prefix_item *item,
 			       void *print_command_item_data)
 {
-	printf(" %2d: %s", i + 1, item->name);
+	if (!item->prefix_length ||
+	    !is_valid_prefix(item->name, item->prefix_length))
+		printf(" %2d: %s", i + 1, item->name);
+	else
+		printf(" %3d: [%.*s]%s", i + 1,
+		       (int)item->prefix_length, item->name,
+		       item->name + item->prefix_length);
 }
 
 struct command_item {
-	struct item item;
+	struct prefix_item item;
 	int (*command)(struct repository *r, const struct pathspec *ps,
 		       struct file_list *files, struct list_options *opts);
 };

@@ -420,7 +464,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 		res = -1;
 
 	for (;;) {
-		i = list_and_choose((struct item **)commands,
+		i = list_and_choose((struct prefix_item **)commands,
 				    ARRAY_SIZE(commands), &main_loop_opts);
 		if (i < -1) {
 			printf(_("Bye.\n"));

index 62ce446dd9..03d0770013 100644
@@ -12,10 +12,12 @@ static int use_color = -1;
 
 enum color_add_i {
 	COLOR_HEADER = 0,
+	COLOR_HELP,
 };
 
 static char list_colors[][COLOR_MAXLEN] = {
 	GIT_COLOR_BOLD,      /* Header */
+	GIT_COLOR_BOLD_RED,  /* Help */
 };
 
 static const char *get_add_i_color(enum color_add_i ix)

@@ -29,6 +31,8 @@ static int parse_color_slot(const char *slot)
 {
 	if (!strcasecmp(slot, "header"))
 		return COLOR_HEADER;
+	if (!strcasecmp(slot, "help"))
+		return COLOR_HELP;
 
 	return -1;
 }

@@ -112,6 +116,7 @@ struct list_and_choose_options {
 	struct list_options list_opts;
 
 	const char *prompt;
+	void (*print_help)(void);
 };
 
 /*

@@ -145,6 +150,11 @@ static ssize_t list_and_choose(struct prefix_item **items, size_t nr,
 		if (!input.len)
 			break;
 
+		if (!strcmp(input.buf, "?")) {
+			opts->print_help();
+			continue;
+		}
+
 		p = input.buf;
 		for (;;) {
 			size_t sep = strcspn(p, " \t\r\n,");

@@ -431,11 +441,23 @@ struct command_item {
 		       struct file_list *files, struct list_options *opts);
 };
 
+static void command_prompt_help(void)
+{
+	const char *help_color = get_add_i_color(COLOR_HELP);
+	color_fprintf_ln(stdout, help_color, "%s", _("Prompt help:"));
+	color_fprintf_ln(stdout, help_color, "1          - %s",
+			 _("select a numbered item"));
+	color_fprintf_ln(stdout, help_color, "foo        - %s",
+			 _("select item based on unique prefix"));
+	color_fprintf_ln(stdout, help_color, "           - %s",
+			 _("(empty) select nothing"));
+}
+
 int run_add_i(struct repository *r, const struct pathspec *ps)
 {
 	struct list_and_choose_options main_loop_opts = {
 		{ 4, N_("*** Commands ***"), print_command_item, NULL },
-		N_("What now")
+		N_("What now"), command_prompt_help
 	};
 	struct command_item
 		status = { { "status" }, run_status };

index 03d0770013..a1550d9b9f 100644
@@ -13,11 +13,17 @@ static int use_color = -1;
 enum color_add_i {
 	COLOR_HEADER = 0,
 	COLOR_HELP,
+	COLOR_PROMPT,
+	COLOR_ERROR,
+	COLOR_RESET,
 };
 
 static char list_colors[][COLOR_MAXLEN] = {
 	GIT_COLOR_BOLD,      /* Header */
 	GIT_COLOR_BOLD_RED,  /* Help */
+	GIT_COLOR_BOLD_BLUE, /* Prompt */
+	GIT_COLOR_BOLD_RED,  /* Error */
+	GIT_COLOR_RESET,     /* Reset */
 };
 
 static const char *get_add_i_color(enum color_add_i ix)

@@ -33,6 +39,12 @@ static int parse_color_slot(const char *slot)
 		return COLOR_HEADER;
 	if (!strcasecmp(slot, "help"))
 		return COLOR_HELP;
+	if (!strcasecmp(slot, "prompt"))
+		return COLOR_PROMPT;
+	if (!strcasecmp(slot, "error"))
+		return COLOR_ERROR;
+	if (!strcasecmp(slot, "reset"))
+		return COLOR_RESET;
 
 	return -1;
 }

@@ -125,6 +137,8 @@ struct list_and_choose_options {
 static ssize_t list_and_choose(struct prefix_item **items, size_t nr,
 			       struct list_and_choose_options *opts)
 {
+	const char *prompt_color = get_add_i_color(COLOR_PROMPT);
+	const char *error_color = get_add_i_color(COLOR_ERROR);
 	struct strbuf input = STRBUF_INIT;
 	ssize_t res = -1;
 

@@ -137,7 +151,8 @@ static ssize_t list_and_choose(struct prefix_item **items, size_t nr,
 
 		list(items, nr, &opts->list_opts);
 
-		printf("%s%s", opts->prompt, "> ");
+		color_fprintf(stdout, prompt_color, "%s", opts->prompt);
+		fputs("> ", stdout);
 		fflush(stdout);
 
 		if (strbuf_getline(&input, stdin) == EOF) {

@@ -178,7 +193,8 @@ static ssize_t list_and_choose(struct prefix_item **items, size_t nr,
 				index = find_unique(p, items, nr);
 
 			if (index < 0 || index >= nr)
-				printf(_("Huh (%s)?\n"), p);
+				color_fprintf_ln(stdout, error_color,
+						 _("Huh (%s)?"), p);
 			else {
 				res = index;
 				break;

@@ -423,15 +439,21 @@ static int run_status(struct repository *r, const struct pathspec *ps,
 	return 0;
 }
 
+struct print_command_item_data {
+	const char *color, *reset;
+};
+
 static void print_command_item(int i, struct prefix_item *item,
 			       void *print_command_item_data)
 {
+	struct print_command_item_data *d = print_command_item_data;
+
 	if (!item->prefix_length ||
 	    !is_valid_prefix(item->name, item->prefix_length))
 		printf(" %2d: %s", i + 1, item->name);
 	else
-		printf(" %3d: [%.*s]%s", i + 1,
-		       (int)item->prefix_length, item->name,
+		printf(" %2d: %s%.*s%s%s", i + 1,
+		       d->color, (int)item->prefix_length, item->name, d->reset,
 		       item->name + item->prefix_length);
 }
 

@@ -455,8 +477,16 @@ static void command_prompt_help(void)
 
 int run_add_i(struct repository *r, const struct pathspec *ps)
 {
+	struct print_command_item_data data = {
+		/*
+		 * When color was asked for, use the prompt color for
+		 * highlighting, otherwise use square brackets.
+		 */
+		want_color(use_color) ? get_add_i_color(COLOR_PROMPT) : "[",
+		want_color(use_color) ? get_add_i_color(COLOR_RESET) : "]"
+	};
 	struct list_and_choose_options main_loop_opts = {
-		{ 4, N_("*** Commands ***"), print_command_item, NULL },
+		{ 4, N_("*** Commands ***"), print_command_item, &data },
 		N_("What now"), command_prompt_help
 	};
 	struct command_item

index a1550d9b9f..a6baf57e20 100644
@@ -439,6 +439,27 @@ static int run_status(struct repository *r, const struct pathspec *ps,
 	return 0;
 }
 
+static int run_help(struct repository *r, const struct pathspec *ps,
+		    struct file_list *files, struct list_options *opts)
+{
+	const char *help_color = get_add_i_color(COLOR_HELP);
+
+	color_fprintf_ln(stdout, help_color, "status        - %s",
+			 _("show paths with changes"));
+	color_fprintf_ln(stdout, help_color, "update        - %s",
+			 _("add working tree state to the staged set of changes"));
+	color_fprintf_ln(stdout, help_color, "revert        - %s",
+			 _("revert staged set of changes back to the HEAD version"));
+	color_fprintf_ln(stdout, help_color, "patch         - %s",
+			 _("pick hunks and update selectively"));
+	color_fprintf_ln(stdout, help_color, "diff          - %s",
+			 _("view diff between HEAD and index"));
+	color_fprintf_ln(stdout, help_color, "add untracked - %s",
+			 _("add contents of untracked files to the staged set of changes"));
+
+	return 0;
+}
+
 struct print_command_item_data {
 	const char *color, *reset;
 };

@@ -490,9 +511,11 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 		N_("What now"), command_prompt_help
 	};
 	struct command_item
-		status = { { "status" }, run_status };
+		status = { { "status" }, run_status },
+		help = { { "help" }, run_help };
 	struct command_item *commands[] = {
-		&status
+		&status,
+		&help
 	};
 
 	struct print_file_item_data print_file_item_data = {

new file mode 100644
index 0000000000..482e458dc6
@@ -0,0 +1,7 @@
+#include "cache.h"
+#include "add-interactive.h"
+
+int run_add_i(struct repository *r, const struct pathspec *ps)
+{
+	die(_("No commands are available in the built-in `git add -i` yet!"));
+}

new file mode 100644
index 0000000000..7043b8741d
@@ -0,0 +1,8 @@
+#ifndef ADD_INTERACTIVE_H
+#define ADD_INTERACTIVE_H
+
+struct repository;
+struct pathspec;
+int run_add_i(struct repository *r, const struct pathspec *ps);
+
+#endif

index db2dfa4350..e19d66e894 100644
@@ -20,6 +20,7 @@
 #include "bulk-checkin.h"
 #include "argv-array.h"
 #include "submodule.h"
+#include "add-interactive.h"
 
 static const char * const builtin_add_usage[] = {
 	N_("git add [<options>] [--] <pathspec>..."),

@@ -185,6 +186,14 @@ int run_add_interactive(const char *revision, const char *patch_mode,
 {
 	int status, i;
 	struct argv_array argv = ARGV_ARRAY_INIT;
+	int use_builtin_add_i =
+		git_env_bool("GIT_TEST_ADD_I_USE_BUILTIN", -1);
+	if (use_builtin_add_i < 0)
+		git_config_get_bool("add.interactive.usebuiltin",
+				    &use_builtin_add_i);
+
+	if (use_builtin_add_i == 1 && !patch_mode)
+		return !!run_add_i(the_repository, pathspec);
 
 	argv_array_push(&argv, "add--interactive");
 	if (patch_mode)

@@ -319,6 +328,7 @@ static int add_config(const char *var, const char *value, void *cb)
 		ignore_add_errors = git_config_bool(var, value);
 		return 0;
 	}
+
 	return git_default_config(var, value, cb);
 }
 

index 5306c48652..daa5f3a736 100644
@@ -2489,22 +2489,6 @@ static void pprint_rename(struct strbuf *name, const char *a, const char *b)
 	}
 }
 
-struct diffstat_t {
-	int nr;
-	int alloc;
-	struct diffstat_file {
-		char *from_name;
-		char *name;
-		char *print_name;
-		const char *comments;
-		unsigned is_unmerged:1;
-		unsigned is_binary:1;
-		unsigned is_renamed:1;
-		unsigned is_interesting:1;
-		uintmax_t added, deleted;
-	} **files;
-};
-
 static struct diffstat_file *diffstat_add(struct diffstat_t *diffstat,
 					  const char *name_a,
 					  const char *name_b)

@@ -6001,12 +5985,7 @@ void diff_flush(struct diff_options *options)
 	    dirstat_by_line) {
 		struct diffstat_t diffstat;
 
-		memset(&diffstat, 0, sizeof(struct diffstat_t));
-		for (i = 0; i < q->nr; i++) {
-			struct diff_filepair *p = q->queue[i];
-			if (check_pair_status(p))
-				diff_flush_stat(p, options, &diffstat);
-		}
+		compute_diffstat(options, &diffstat, q);
 		if (output_format & DIFF_FORMAT_NUMSTAT)
 			show_numstat(&diffstat, options);
 		if (output_format & DIFF_FORMAT_DIFFSTAT)

@@ -6306,6 +6285,20 @@ static int is_submodule_ignored(const char *path, struct diff_options *options)
 	return ignored;
 }
 
+void compute_diffstat(struct diff_options *options,
+		      struct diffstat_t *diffstat,
+		      struct diff_queue_struct *q)
+{
+	int i;
+
+	memset(diffstat, 0, sizeof(struct diffstat_t));
+	for (i = 0; i < q->nr; i++) {
+		struct diff_filepair *p = q->queue[i];
+		if (check_pair_status(p))
+			diff_flush_stat(p, options, diffstat);
+	}
+}
+
 void diff_addremove(struct diff_options *options,
 		    int addremove, unsigned mode,
 		    const struct object_id *oid,

index b512d0477a..ae9bedfab8 100644
@@ -240,6 +240,22 @@ void diff_emit_submodule_error(struct diff_options *o, const char *err);
 void diff_emit_submodule_pipethrough(struct diff_options *o,
 				     const char *line, int len);
 
+struct diffstat_t {
+	int nr;
+	int alloc;
+	struct diffstat_file {
+		char *from_name;
+		char *name;
+		char *print_name;
+		const char *comments;
+		unsigned is_unmerged:1;
+		unsigned is_binary:1;
+		unsigned is_renamed:1;
+		unsigned is_interesting:1;
+		uintmax_t added, deleted;
+	} **files;
+};
+
 enum color_diff {
 	DIFF_RESET = 0,
 	DIFF_CONTEXT = 1,

@@ -328,6 +344,9 @@ void diff_change(struct diff_options *,
 
 struct diff_filepair *diff_unmerge(struct diff_options *, const char *path);
 
+void compute_diffstat(struct diff_options *options, struct diffstat_t *diffstat,
+		      struct diff_queue_struct *q);
+
 #define DIFF_SETUP_REVERSE      	1
 #define DIFF_SETUP_USE_SIZE_CACHE	4
 

index 482e458dc6..59b28011f7 100644
@@ -1,7 +1,270 @@
 #include "cache.h"
 #include "add-interactive.h"
+#include "diffcore.h"
+#include "revision.h"
+#include "refs.h"
+
+struct item {
+	const char *name;
+};
+
+struct list_options {
+	const char *header;
+	void (*print_item)(int i, struct item *item, void *print_item_data);
+	void *print_item_data;
+};
+
+static void list(struct item **list, size_t nr, struct list_options *opts)
+{
+	int i;
+
+	if (!nr)
+		return;
+
+	if (opts->header)
+		printf("%s\n", opts->header);
+
+	for (i = 0; i < nr; i++) {
+		opts->print_item(i, list[i], opts->print_item_data);
+		putchar('\n');
+	}
+}
+
+struct adddel {
+	uintmax_t add, del;
+	unsigned seen:1, binary:1;
+};
+
+struct file_list {
+	struct file_item {
+		struct item item;
+		struct adddel index, worktree;
+	} **file;
+	size_t nr, alloc;
+};
+
+static void add_file_item(struct file_list *list, const char *name)
+{
+	struct file_item *item;
+
+	FLEXPTR_ALLOC_STR(item, item.name, name);
+
+	ALLOC_GROW(list->file, list->nr + 1, list->alloc);
+	list->file[list->nr++] = item;
+}
+
+static void reset_file_list(struct file_list *list)
+{
+	size_t i;
+
+	for (i = 0; i < list->nr; i++)
+		free(list->file[i]);
+	list->nr = 0;
+}
+
+static void release_file_list(struct file_list *list)
+{
+	reset_file_list(list);
+	FREE_AND_NULL(list->file);
+	list->alloc = 0;
+}
+
+static int file_item_cmp(const void *a, const void *b)
+{
+	const struct file_item * const *f1 = a;
+	const struct file_item * const *f2 = b;
+
+	return strcmp((*f1)->item.name, (*f2)->item.name);
+}
+
+struct pathname_entry {
+	struct hashmap_entry ent;
+	size_t index;
+	char pathname[FLEX_ARRAY];
+};
+
+static int pathname_entry_cmp(const void *unused_cmp_data,
+			      const void *entry, const void *entry_or_key,
+			      const void *pathname)
+{
+	const struct pathname_entry *e1 = entry, *e2 = entry_or_key;
+
+	return strcmp(e1->pathname,
+		      pathname ? (const char *)pathname : e2->pathname);
+}
+
+struct collection_status {
+	enum { FROM_WORKTREE = 0, FROM_INDEX = 1 } phase;
+
+	const char *reference;
+
+	struct file_list *list;
+	struct hashmap file_map;
+};
+
+static void collect_changes_cb(struct diff_queue_struct *q,
+			       struct diff_options *options,
+			       void *data)
+{
+	struct collection_status *s = data;
+	struct diffstat_t stat = { 0 };
+	int i;
+
+	if (!q->nr)
+		return;
+
+	compute_diffstat(options, &stat, q);
+
+	for (i = 0; i < stat.nr; i++) {
+		const char *name = stat.files[i]->name;
+		int hash = strhash(name);
+		struct pathname_entry *entry;
+		size_t file_index;
+		struct file_item *file;
+		struct adddel *adddel;
+
+		entry = hashmap_get_from_hash(&s->file_map, hash, name);
+		if (entry)
+			file_index = entry->index;
+		else {
+			FLEX_ALLOC_STR(entry, pathname, name);
+			hashmap_entry_init(entry, hash);
+			entry->index = file_index = s->list->nr;
+			hashmap_add(&s->file_map, entry);
+
+			add_file_item(s->list, name);
+		}
+		file = s->list->file[file_index];
+
+		adddel = s->phase == FROM_INDEX ? &file->index : &file->worktree;
+		adddel->seen = 1;
+		adddel->add = stat.files[i]->added;
+		adddel->del = stat.files[i]->deleted;
+		if (stat.files[i]->is_binary)
+			adddel->binary = 1;
+	}
+}
+
+static int get_modified_files(struct repository *r, struct file_list *list,
+			      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 };
+
+	if (repo_read_index_preload(r, ps, 0) < 0)
+		return error(_("could not read index"));
+
+	s.list = list;
+	hashmap_init(&s.file_map, pathname_entry_cmp, NULL, 0);
+
+	for (s.phase = FROM_WORKTREE; s.phase <= FROM_INDEX; s.phase++) {
+		struct rev_info rev;
+		struct setup_revision_opt opt = { 0 };
+
+		opt.def = is_initial ?
+			empty_tree_oid_hex() : oid_to_hex(&head_oid);
+
+		init_revisions(&rev, NULL);
+		setup_revisions(0, NULL, &rev, &opt);
+
+		rev.diffopt.output_format = DIFF_FORMAT_CALLBACK;
+		rev.diffopt.format_callback = collect_changes_cb;
+		rev.diffopt.format_callback_data = &s;
+
+		if (ps)
+			copy_pathspec(&rev.prune_data, ps);
+
+		if (s.phase == FROM_INDEX)
+			run_diff_index(&rev, 1);
+		else {
+			rev.diffopt.flags.ignore_dirty_submodules = 1;
+			run_diff_files(&rev, 0);
+		}
+	}
+	hashmap_free(&s.file_map, 1);
+
+	/* While the diffs are ordered already, we ran *two* diffs... */
+	QSORT(list->file, list->nr, file_item_cmp);
+
+	return 0;
+}
+
+static void populate_wi_changes(struct strbuf *buf,
+				struct adddel *ad, const char *no_changes)
+{
+	if (ad->binary)
+		strbuf_addstr(buf, _("binary"));
+	else if (ad->seen)
+		strbuf_addf(buf, "+%"PRIuMAX"/-%"PRIuMAX,
+			    (uintmax_t)ad->add, (uintmax_t)ad->del);
+	else
+		strbuf_addstr(buf, no_changes);
+}
+
+struct print_file_item_data {
+	const char *modified_fmt;
+	struct strbuf buf, index, worktree;
+};
+
+static void print_file_item(int i, struct item *item,
+			    void *print_file_item_data)
+{
+	struct file_item *c = (struct file_item *)item;
+	struct print_file_item_data *d = print_file_item_data;
+
+	strbuf_reset(&d->index);
+	strbuf_reset(&d->worktree);
+	strbuf_reset(&d->buf);
+
+	populate_wi_changes(&d->worktree, &c->worktree, _("nothing"));
+	populate_wi_changes(&d->index, &c->index, _("unchanged"));
+	strbuf_addf(&d->buf, d->modified_fmt,
+		    d->index.buf, d->worktree.buf, item->name);
+
+	printf(" %2d: %s", i + 1, d->buf.buf);
+}
+
+static int run_status(struct repository *r, const struct pathspec *ps,
+		      struct file_list *files, struct list_options *opts)
+{
+	reset_file_list(files);
+
+	if (get_modified_files(r, files, ps) < 0)
+		return -1;
+
+	if (files->nr)
+		list((struct item **)files->file, files->nr, opts);
+	putchar('\n');
+
+	return 0;
+}
 
 int run_add_i(struct repository *r, const struct pathspec *ps)
 {
-	die(_("No commands are available in the built-in `git add -i` yet!"));
+	struct print_file_item_data print_file_item_data = {
+		"%12s %12s %s", STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
+	};
+	struct list_options opts = {
+		NULL, print_file_item, &print_file_item_data
+	};
+	struct strbuf header = STRBUF_INIT;
+	struct file_list files = { NULL };
+	int res = 0;
+
+	strbuf_addstr(&header, "      ");
+	strbuf_addf(&header, print_file_item_data.modified_fmt,
+		    _("staged"), _("unstaged"), _("path"));
+	opts.header = header.buf;
+
+	res = run_status(r, ps, &files, &opts);
+
+	release_file_list(&files);
+	strbuf_release(&print_file_item_data.buf);
+	strbuf_release(&print_file_item_data.index);
+	strbuf_release(&print_file_item_data.worktree);
+	strbuf_release(&header);
+
+	return res;
 }

index 59b28011f7..2dbf29dee2 100644
@@ -258,7 +258,9 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 		    _("staged"), _("unstaged"), _("path"));
 	opts.header = header.buf;
 
-	res = run_status(r, ps, &files, &opts);
+	repo_refresh_and_write_index(r, REFRESH_QUIET, 1);
+	if (run_status(r, ps, &files, &opts) < 0)
+		res = -1;
 
 	release_file_list(&files);
 	strbuf_release(&print_file_item_data.buf);

index 65e6f8b8fd..c90f310093 100644
@@ -272,3 +272,22 @@ int repo_hold_locked_index(struct repository *repo,
 		BUG("the repo hasn't been setup");
 	return hold_lock_file_for_update(lf, repo->index_file, flags);
 }
+
+int repo_refresh_and_write_index(struct repository *r,
+				 unsigned int flags, int gentle)
+{
+	struct lock_file lock_file = LOCK_INIT;
+	int fd;
+
+	if (repo_read_index_preload(r, NULL, 0) < 0)
+		return error(_("could not read index"));
+	fd = repo_hold_locked_index(r, &lock_file, 0);
+	if (!gentle && fd < 0)
+		return error(_("could not lock index for writing"));
+	refresh_index(r->index, flags, NULL, NULL, NULL);
+	if (0 <= fd)
+		repo_update_index_if_able(r, &lock_file);
+	rollback_lock_file(&lock_file);
+
+	return 0;
+}

index 8981649d43..fb49e0e328 100644
@@ -154,5 +154,12 @@ int repo_read_index_unmerged(struct repository *);
  */
 void repo_update_index_if_able(struct repository *, struct lock_file *);
 
+/*
+ * Refresh the index and write it out. If the index file could not be
+ * locked, error out, except in gentle mode. The flags will be passed
+ * through to refresh_index().
+ */
+int repo_refresh_and_write_index(struct repository *r,
+				 unsigned int flags, int gentle);
 
 #endif /* REPOSITORY_H */

index 2dbf29dee2..6c2fca12c1 100644
@@ -1,9 +1,51 @@
 #include "cache.h"
 #include "add-interactive.h"
+#include "color.h"
+#include "config.h"
 #include "diffcore.h"
 #include "revision.h"
 #include "refs.h"
 
+struct add_i_state {
+	struct repository *r;
+	int use_color;
+	char header_color[COLOR_MAXLEN];
+};
+
+static void init_color(struct repository *r, struct add_i_state *s,
+		       const char *slot_name, char *dst,
+		       const char *default_color)
+{
+	char *key = xstrfmt("color.interactive.%s", slot_name);
+	const char *value;
+
+	if (!s->use_color)
+		dst[0] = '\0';
+	else if (repo_config_get_value(r, key, &value) ||
+		 color_parse(value, dst))
+		strlcpy(dst, default_color, COLOR_MAXLEN);
+
+	free(key);
+}
+
+static int init_add_i_state(struct repository *r, struct add_i_state *s)
+{
+	const char *value;
+
+	s->r = r;
+
+	if (repo_config_get_value(r, "color.interactive", &value))
+		s->use_color = -1;
+	else
+		s->use_color =
+			git_config_colorbool("color.interactive", value);
+	s->use_color = want_color(s->use_color);
+
+	init_color(r, s, "header", s->header_color, GIT_COLOR_BOLD);
+
+	return 0;
+}
+
 struct item {
 	const char *name;
 };

@@ -14,7 +56,8 @@ struct list_options {
 	void *print_item_data;
 };
 
-static void list(struct item **list, size_t nr, struct list_options *opts)
+static void list(struct item **list, size_t nr,
+		 struct add_i_state *s, struct list_options *opts)
 {
 	int i;
 

@@ -22,7 +65,8 @@ static void list(struct item **list, size_t nr, struct list_options *opts)
 		return;
 
 	if (opts->header)
-		printf("%s\n", opts->header);
+		color_fprintf_ln(stdout, s->header_color,
+				 "%s", opts->header);
 
 	for (i = 0; i < nr; i++) {
 		opts->print_item(i, list[i], opts->print_item_data);

@@ -226,16 +270,16 @@ static void print_file_item(int i, struct item *item,
 	printf(" %2d: %s", i + 1, d->buf.buf);
 }
 
-static int run_status(struct repository *r, const struct pathspec *ps,
+static int run_status(struct add_i_state *s, const struct pathspec *ps,
 		      struct file_list *files, struct list_options *opts)
 {
 	reset_file_list(files);
 
-	if (get_modified_files(r, files, ps) < 0)
+	if (get_modified_files(s->r, files, ps) < 0)
 		return -1;
 
 	if (files->nr)
-		list((struct item **)files->file, files->nr, opts);
+		list((struct item **)files->file, files->nr, s, opts);
 	putchar('\n');
 
 	return 0;

@@ -243,6 +287,7 @@ static int run_status(struct repository *r, const struct pathspec *ps,
 
 int run_add_i(struct repository *r, const struct pathspec *ps)
 {
+	struct add_i_state s = { NULL };
 	struct print_file_item_data print_file_item_data = {
 		"%12s %12s %s", STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
 	};

@@ -253,13 +298,16 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 	struct file_list files = { NULL };
 	int res = 0;
 
+	if (init_add_i_state(r, &s))
+		return error("could not parse `add -i` config");
+
 	strbuf_addstr(&header, "      ");
 	strbuf_addf(&header, print_file_item_data.modified_fmt,
 		    _("staged"), _("unstaged"), _("path"));
 	opts.header = header.buf;
 
 	repo_refresh_and_write_index(r, REFRESH_QUIET, 1);
-	if (run_status(r, ps, &files, &opts) < 0)
+	if (run_status(&s, ps, &files, &opts) < 0)
 		res = -1;
 
 	release_file_list(&files);

index 6c2fca12c1..0ea4f3edb8 100644
@@ -51,6 +51,7 @@ struct item {
 };
 
 struct list_options {
+	int columns;
 	const char *header;
 	void (*print_item)(int i, struct item *item, void *print_item_data);
 	void *print_item_data;

@@ -59,7 +60,7 @@ struct list_options {
 static void list(struct item **list, size_t nr,
 		 struct add_i_state *s, struct list_options *opts)
 {
-	int i;
+	int i, last_lf = 0;
 
 	if (!nr)
 		return;

@@ -70,8 +71,97 @@ static void list(struct item **list, size_t nr,
 
 	for (i = 0; i < nr; i++) {
 		opts->print_item(i, list[i], opts->print_item_data);
+
+		if ((opts->columns) && ((i + 1) % (opts->columns))) {
+			putchar('\t');
+			last_lf = 0;
+		}
+		else {
+			putchar('\n');
+			last_lf = 1;
+		}
+	}
+
+	if (!last_lf)
 		putchar('\n');
+}
+struct list_and_choose_options {
+	struct list_options list_opts;
+
+	const char *prompt;
+};
+
+#define LIST_AND_CHOOSE_ERROR (-1)
+#define LIST_AND_CHOOSE_QUIT  (-2)
+
+/*
+ * Returns the selected index.
+ *
+ * If an error occurred, returns `LIST_AND_CHOOSE_ERROR`. Upon EOF,
+ * `LIST_AND_CHOOSE_QUIT` is returned.
+ */
+static ssize_t list_and_choose(struct item **items, size_t nr,
+			       struct add_i_state *s,
+			       struct list_and_choose_options *opts)
+{
+	struct strbuf input = STRBUF_INIT;
+	ssize_t res = LIST_AND_CHOOSE_ERROR;
+
+	for (;;) {
+		char *p, *endp;
+
+		strbuf_reset(&input);
+
+		list(items, nr, s, &opts->list_opts);
+
+		printf("%s%s", opts->prompt, "> ");
+		fflush(stdout);
+
+		if (strbuf_getline(&input, stdin) == EOF) {
+			putchar('\n');
+			res = LIST_AND_CHOOSE_QUIT;
+			break;
+		}
+		strbuf_trim(&input);
+
+		if (!input.len)
+			break;
+
+		p = input.buf;
+		for (;;) {
+			size_t sep = strcspn(p, " \t\r\n,");
+			ssize_t index = -1;
+
+			if (!sep) {
+				if (!*p)
+					break;
+				p++;
+				continue;
+			}
+
+			if (isdigit(*p)) {
+				index = strtoul(p, &endp, 10) - 1;
+				if (endp != p + sep)
+					index = -1;
+			}
+
+			p[sep] = '\0';
+			if (index < 0 || index >= nr)
+				printf(_("Huh (%s)?\n"), p);
+			else {
+				res = index;
+				break;
+			}
+
+			p += sep + 1;
+		}
+
+		if (res != LIST_AND_CHOOSE_ERROR)
+			break;
 	}
+
+	strbuf_release(&input);
+	return res;
 }
 
 struct adddel {

@@ -285,17 +375,40 @@ static int run_status(struct add_i_state *s, const struct pathspec *ps,
 	return 0;
 }
 
+static void print_command_item(int i, struct item *item,
+			       void *print_command_item_data)
+{
+	printf(" %2d: %s", i + 1, item->name);
+}
+
+struct command_item {
+	struct item item;
+	int (*command)(struct add_i_state *s, const struct pathspec *ps,
+		       struct file_list *files, struct list_options *opts);
+};
+
 int run_add_i(struct repository *r, const struct pathspec *ps)
 {
 	struct add_i_state s = { NULL };
+	struct list_and_choose_options main_loop_opts = {
+		{ 4, N_("*** Commands ***"), print_command_item, NULL },
+		N_("What now")
+	};
+	struct command_item
+		status = { { "status" }, run_status };
+	struct command_item *commands[] = {
+		&status
+	};
+
 	struct print_file_item_data print_file_item_data = {
 		"%12s %12s %s", STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
 	};
 	struct list_options opts = {
-		NULL, print_file_item, &print_file_item_data
+		0, NULL, print_file_item, &print_file_item_data
 	};
 	struct strbuf header = STRBUF_INIT;
 	struct file_list files = { NULL };
+	ssize_t i;
 	int res = 0;
 
 	if (init_add_i_state(r, &s))

@@ -310,6 +423,18 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 	if (run_status(&s, ps, &files, &opts) < 0)
 		res = -1;
 
+	for (;;) {
+		i = list_and_choose((struct item **)commands,
+				    ARRAY_SIZE(commands), &s, &main_loop_opts);
+		if (i == LIST_AND_CHOOSE_QUIT) {
+			printf(_("Bye.\n"));
+			res = 0;
+			break;
+		}
+		if (i != LIST_AND_CHOOSE_ERROR)
+			res = commands[i]->command(&s, ps, &files, &opts);
+	}
+
 	release_file_list(&files);
 	strbuf_release(&print_file_item_data.buf);
 	strbuf_release(&print_file_item_data.index);