diff --git a/.gitignore b/.gitignore
index d706dd92c6a63474616c09388fc9744ff055cedc..91e69665f46bdecaedd4a9664e5238448b42467a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,7 @@ GIT-CFLAGS
 GIT-VERSION-FILE
 git
 git-add
+git-add--interactive
 git-am
 git-annotate
 git-apply
diff --git a/Makefile b/Makefile
index 8919dabc781867e121238dd8dd0a05a8ac02586e..354f66b23335ba08f13813e64f8360015871867a 100644
--- a/Makefile
+++ b/Makefile
@@ -177,6 +177,7 @@ SCRIPT_SH = \
 	git-lost-found.sh git-quiltimport.sh
 
 SCRIPT_PERL = \
+	git-add--interactive.perl \
 	git-archimport.perl git-cvsimport.perl git-relink.perl \
 	git-rerere.perl \
 	git-cvsserver.perl \
diff --git a/builtin-add.c b/builtin-add.c
index b3f920676a958e581c55dcca48e9a8f01b43859b..aa2f0f32af938dc033d40fc0e909b208b3781120 100644
--- a/builtin-add.c
+++ b/builtin-add.c
@@ -8,6 +8,7 @@
 #include "cache.h"
 #include "builtin.h"
 #include "dir.h"
+#include "exec_cmd.h"
 #include "cache-tree.h"
 
 static const char builtin_add_usage[] =
@@ -89,6 +90,20 @@ int cmd_add(int argc, const char **argv, const char *prefix)
 	int verbose = 0, show_only = 0;
 	const char **pathspec;
 	struct dir_struct dir;
+	int add_interactive = 0;
+
+	for (i = 1; i < argc; i++) {
+		if (!strcmp("--interactive", argv[i]))
+			add_interactive++;
+	}
+	if (add_interactive) {
+		const char *args[] = { "add--interactive", NULL };
+
+		if (add_interactive != 1 || argc != 2)
+			die("add --interactive does not take any parameters");
+		execv_git_cmd(args);
+		exit(1);
+	}
 
 	git_config(git_default_config);
 
diff --git a/git-add--interactive.perl b/git-add--interactive.perl
new file mode 100755
index 0000000000000000000000000000000000000000..83d017d23ceb5a634e8d8e79b154dd1d7e79d640
--- /dev/null
+++ b/git-add--interactive.perl
@@ -0,0 +1,570 @@
+#!/usr/bin/perl -w
+
+use strict;
+
+sub run_cmd_pipe {
+	my $fh = undef;
+	open($fh, '-|', @_) or die;
+	return <$fh>;
+}
+
+my ($GIT_DIR) = run_cmd_pipe(qw(git rev-parse --git-dir));
+
+if (!defined $GIT_DIR) {
+	exit(1); # rev-parse would have already said "not a git repo"
+}
+chomp($GIT_DIR);
+
+sub refresh {
+	my $fh;
+	open $fh, '-|', qw(git update-index --refresh)
+	    or die;
+	while (<$fh>) {
+		;# ignore 'needs update'
+	}
+	close $fh;
+}
+
+sub list_untracked {
+	map {
+		chomp $_;
+		$_;
+	}
+	run_cmd_pipe(qw(git ls-files --others
+			--exclude-per-directory=.gitignore),
+		     "--exclude-from=$GIT_DIR/info/exclude",
+		     '--', @_);
+}
+
+my $status_fmt = '%12s %12s %s';
+my $status_head = sprintf($status_fmt, 'staged', 'unstaged', 'path');
+
+# Returns list of hashes, contents of each of which are:
+# PRINT:	print message
+# VALUE:	pathname
+# BINARY:	is a binary path
+# INDEX:	is index different from HEAD?
+# FILE:		is file different from index?
+# INDEX_ADDDEL:	is it add/delete between HEAD and index?
+# FILE_ADDDEL:	is it add/delete between index and file?
+
+sub list_modified {
+	my ($only) = @_;
+	my (%data, @return);
+	my ($add, $del, $adddel, $file);
+
+	for (run_cmd_pipe(qw(git diff-index --cached
+			     --numstat --summary HEAD))) {
+		if (($add, $del, $file) =
+		    /^([-\d]+)	([-\d]+)	(.*)/) {
+			my ($change, $bin);
+			if ($add eq '-' && $del eq '-') {
+				$change = 'binary';
+				$bin = 1;
+			}
+			else {
+				$change = "+$add/-$del";
+			}
+			$data{$file} = {
+				INDEX => $change,
+				BINARY => $bin,
+				FILE => 'nothing',
+			}
+		}
+		elsif (($adddel, $file) =
+		       /^ (create|delete) mode [0-7]+ (.*)$/) {
+			$data{$file}{INDEX_ADDDEL} = $adddel;
+		}
+	}
+
+	for (run_cmd_pipe(qw(git diff-files --numstat --summary))) {
+		if (($add, $del, $file) =
+		    /^([-\d]+)	([-\d]+)	(.*)/) {
+			if (!exists $data{$file}) {
+				$data{$file} = +{
+					INDEX => 'unchanged',
+					BINARY => 0,
+				};
+			}
+			my ($change, $bin);
+			if ($add eq '-' && $del eq '-') {
+				$change = 'binary';
+				$bin = 1;
+			}
+			else {
+				$change = "+$add/-$del";
+			}
+			$data{$file}{FILE} = $change;
+			if ($bin) {
+				$data{$file}{BINARY} = 1;
+			}
+		}
+		elsif (($adddel, $file) =
+		       /^ (create|delete) mode [0-7]+ (.*)$/) {
+			$data{$file}{FILE_ADDDEL} = $adddel;
+		}
+	}
+
+	for (sort keys %data) {
+		my $it = $data{$_};
+
+		if ($only) {
+			if ($only eq 'index-only') {
+				next if ($it->{INDEX} eq 'unchanged');
+			}
+			if ($only eq 'file-only') {
+				next if ($it->{FILE} eq 'nothing');
+			}
+		}
+		push @return, +{
+			VALUE => $_,
+			PRINT => (sprintf $status_fmt,
+				  $it->{INDEX}, $it->{FILE}, $_),
+			%$it,
+		};
+	}
+	return @return;
+}
+
+sub find_unique {
+	my ($string, @stuff) = @_;
+	my $found = undef;
+	for (my $i = 0; $i < @stuff; $i++) {
+		my $it = $stuff[$i];
+		my $hit = undef;
+		if (ref $it) {
+			if ((ref $it) eq 'ARRAY') {
+				$it = $it->[0];
+			}
+			else {
+				$it = $it->{VALUE};
+			}
+		}
+		eval {
+			if ($it =~ /^$string/) {
+				$hit = 1;
+			};
+		};
+		if (defined $hit && defined $found) {
+			return undef;
+		}
+		if ($hit) {
+			$found = $i + 1;
+		}
+	}
+	return $found;
+}
+
+sub list_and_choose {
+	my ($opts, @stuff) = @_;
+	my (@chosen, @return);
+	my $i;
+
+      TOPLOOP:
+	while (1) {
+		my $last_lf = 0;
+
+		if ($opts->{HEADER}) {
+			if (!$opts->{LIST_FLAT}) {
+				print "     ";
+			}
+			print "$opts->{HEADER}\n";
+		}
+		for ($i = 0; $i < @stuff; $i++) {
+			my $chosen = $chosen[$i] ? '*' : ' ';
+			my $print = $stuff[$i];
+			if (ref $print) {
+				if ((ref $print) eq 'ARRAY') {
+					$print = $print->[0];
+				}
+				else {
+					$print = $print->{PRINT};
+				}
+			}
+			printf("%s%2d: %s", $chosen, $i+1, $print);
+			if (($opts->{LIST_FLAT}) &&
+			    (($i + 1) % ($opts->{LIST_FLAT}))) {
+				print "\t";
+				$last_lf = 0;
+			}
+			else {
+				print "\n";
+				$last_lf = 1;
+			}
+		}
+		if (!$last_lf) {
+			print "\n";
+		}
+
+		return if ($opts->{LIST_ONLY});
+
+		print $opts->{PROMPT};
+		if ($opts->{SINGLETON}) {
+			print "> ";
+		}
+		else {
+			print ">> ";
+		}
+		my $line = <STDIN>;
+		last if (!$line);
+		chomp $line;
+		my $donesomething = 0;
+		for my $choice (split(/[\s,]+/, $line)) {
+			my $choose = 1;
+			my ($bottom, $top);
+
+			# Input that begins with '-'; unchoose
+			if ($choice =~ s/^-//) {
+				$choose = 0;
+			}
+			# A range can be specified like 5-7
+			if ($choice =~ /^(\d+)-(\d+)$/) {
+				($bottom, $top) = ($1, $2);
+			}
+			elsif ($choice =~ /^\d+$/) {
+				$bottom = $top = $choice;
+			}
+			elsif ($choice eq '*') {
+				$bottom = 1;
+				$top = 1 + @stuff;
+			}
+			else {
+				$bottom = $top = find_unique($choice, @stuff);
+				if (!defined $bottom) {
+					print "Huh ($choice)?\n";
+					next TOPLOOP;
+				}
+			}
+			if ($opts->{SINGLETON} && $bottom != $top) {
+				print "Huh ($choice)?\n";
+				next TOPLOOP;
+			}
+			for ($i = $bottom-1; $i <= $top-1; $i++) {
+				next if (@stuff <= $i);
+				$chosen[$i] = $choose;
+				$donesomething++;
+			}
+		}
+		last if (!$donesomething || $opts->{IMMEDIATE});
+	}
+	for ($i = 0; $i < @stuff; $i++) {
+		if ($chosen[$i]) {
+			push @return, $stuff[$i];
+		}
+	}
+	return @return;
+}
+
+sub status_cmd {
+	list_and_choose({ LIST_ONLY => 1, HEADER => $status_head },
+			list_modified());
+	print "\n";
+}
+
+sub say_n_paths {
+	my $did = shift @_;
+	my $cnt = scalar @_;
+	print "$did ";
+	if (1 < $cnt) {
+		print "$cnt paths\n";
+	}
+	else {
+		print "one path\n";
+	}
+}
+
+sub update_cmd {
+	my @mods = list_modified('file-only');
+	return if (!@mods);
+
+	my @update = list_and_choose({ PROMPT => 'Update',
+				       HEADER => $status_head, },
+				     @mods);
+	if (@update) {
+		system(qw(git update-index --add --),
+		       map { $_->{VALUE} } @update);
+		say_n_paths('updated', @update);
+	}
+	print "\n";
+}
+
+sub revert_cmd {
+	my @update = list_and_choose({ PROMPT => 'Revert',
+				       HEADER => $status_head, },
+				     list_modified());
+	if (@update) {
+		my @lines = run_cmd_pipe(qw(git ls-tree HEAD --),
+					 map { $_->{VALUE} } @update);
+		my $fh;
+		open $fh, '|-', qw(git update-index --index-info)
+		    or die;
+		for (@lines) {
+			print $fh $_;
+		}
+		close($fh);
+		for (@update) {
+			if ($_->{INDEX_ADDDEL} &&
+			    $_->{INDEX_ADDDEL} eq 'create') {
+				system(qw(git update-index --force-remove --),
+				       $_->{VALUE});
+				print "note: $_->{VALUE} is untracked now.\n";
+			}
+		}
+		refresh();
+		say_n_paths('reverted', @update);
+	}
+	print "\n";
+}
+
+sub add_untracked_cmd {
+	my @add = list_and_choose({ PROMPT => 'Add untracked' },
+				  list_untracked());
+	if (@add) {
+		system(qw(git update-index --add --), @add);
+		say_n_paths('added', @add);
+	}
+	print "\n";
+}
+
+sub parse_diff {
+	my ($path) = @_;
+	my @diff = run_cmd_pipe(qw(git diff-files -p --), $path);
+	my (@hunk) = { TEXT => [] };
+
+	for (@diff) {
+		if (/^@@ /) {
+			push @hunk, { TEXT => [] };
+		}
+		push @{$hunk[-1]{TEXT}}, $_;
+	}
+	return @hunk;
+}
+
+sub help_patch_cmd {
+	print <<\EOF ;
+y - stage this hunk
+n - do not stage this hunk
+a - stage this and all the remaining hunks
+d - do not stage this hunk nor any of the remaining hunks
+j - leave this hunk undecided, see next undecided hunk
+J - leave this hunk undecided, see next hunk
+k - leave this hunk undecided, see previous undecided hunk
+K - leave this hunk undecided, see previous hunk
+EOF
+}
+
+sub patch_update_cmd {
+	my @mods = list_modified('file-only');
+	@mods = grep { !($_->{BINARY}) } @mods;
+	return if (!@mods);
+
+	my ($it) = list_and_choose({ PROMPT => 'Patch update',
+				     SINGLETON => 1,
+				     IMMEDIATE => 1,
+				     HEADER => $status_head, },
+				   @mods);
+	return if (!$it);
+
+	my ($ix, $num);
+	my $path = $it->{VALUE};
+	my ($head, @hunk) = parse_diff($path);
+	for (@{$head->{TEXT}}) {
+		print;
+	}
+	$num = scalar @hunk;
+	$ix = 0;
+
+	while (1) {
+		my ($prev, $next, $other, $undecided);
+		$other = '';
+
+		if ($num <= $ix) {
+			$ix = 0;
+		}
+		for (my $i = 0; $i < $ix; $i++) {
+			if (!defined $hunk[$i]{USE}) {
+				$prev = 1;
+				$other .= '/k';
+				last;
+			}
+		}
+		if ($ix) {
+			$other .= '/K';
+		}
+		for (my $i = $ix + 1; $i < $num; $i++) {
+			if (!defined $hunk[$i]{USE}) {
+				$next = 1;
+				$other .= '/j';
+				last;
+			}
+		}
+		if ($ix < $num - 1) {
+			$other .= '/J';
+		}
+		for (my $i = 0; $i < $num; $i++) {
+			if (!defined $hunk[$i]{USE}) {
+				$undecided = 1;
+				last;
+			}
+		}
+		last if (!$undecided);
+
+		for (@{$hunk[$ix]{TEXT}}) {
+			print;
+		}
+		print "Stage this hunk [y/n/a/d$other/?]? ";
+		my $line = <STDIN>;
+		if ($line) {
+			if ($line =~ /^y/i) {
+				$hunk[$ix]{USE} = 1;
+			}
+			elsif ($line =~ /^n/i) {
+				$hunk[$ix]{USE} = 0;
+			}
+			elsif ($line =~ /^a/i) {
+				while ($ix < $num) {
+					if (!defined $hunk[$ix]{USE}) {
+						$hunk[$ix]{USE} = 1;
+					}
+					$ix++;
+				}
+				next;
+			}
+			elsif ($line =~ /^d/i) {
+				while ($ix < $num) {
+					if (!defined $hunk[$ix]{USE}) {
+						$hunk[$ix]{USE} = 0;
+					}
+					$ix++;
+				}
+				next;
+			}
+			elsif ($other =~ /K/ && $line =~ /^K/) {
+				$ix--;
+				next;
+			}
+			elsif ($other =~ /J/ && $line =~ /^J/) {
+				$ix++;
+				next;
+			}
+			elsif ($other =~ /k/ && $line =~ /^k/) {
+				while (1) {
+					$ix--;
+					last if (!$ix ||
+						 !defined $hunk[$ix]{USE});
+				}
+				next;
+			}
+			elsif ($other =~ /j/ && $line =~ /^j/) {
+				while (1) {
+					$ix++;
+					last if ($ix >= $num ||
+						 !defined $hunk[$ix]{USE});
+				}
+				next;
+			}
+			else {
+				help_patch_cmd($other);
+				next;
+			}
+			# soft increment
+			while (1) {
+				$ix++;
+				last if ($ix >= $num ||
+					 !defined $hunk[$ix]{USE});
+			}
+		}
+	}
+
+	my ($o_lno, $n_lno);
+	my @result = ();
+	for (@hunk) {
+		my $text = $_->{TEXT};
+		my ($o_ofs, $o_cnt, $n_ofs, $n_cnt) =
+		    $text->[0] =~ /^@@ -(\d+)(?:,(\d+)) \+(\d+)(?:,(\d+)) @@/;
+		if (!$_->{USE}) {
+			# Adjust offset here.
+			next;
+		}
+		else {
+			for (@$text) {
+				push @result, $_;
+			}
+		}
+	}
+
+	if (@result) {
+		my $fh;
+
+		open $fh, '|-', qw(git apply --cached);
+		for (@{$head->{TEXT}}, @result) {
+			print $fh $_;
+		}
+		close $fh;
+		refresh();
+	}
+
+	print "\n";
+}
+
+sub diff_cmd {
+	my @mods = list_modified('index-only');
+	@mods = grep { !($_->{BINARY}) } @mods;
+	return if (!@mods);
+	my (@them) = list_and_choose({ PROMPT => 'Review diff',
+				     IMMEDIATE => 1,
+				     HEADER => $status_head, },
+				   @mods);
+	return if (!@them);
+	system(qw(git diff-index -p --cached HEAD --),
+	       map { $_->{VALUE} } @them);
+}
+
+sub quit_cmd {
+	print "Bye.\n";
+	exit(0);
+}
+
+sub help_cmd {
+	print <<\EOF ;
+status        - show paths with changes
+update        - add working tree state to the staged set of changes
+revert        - revert staged set of changes back to the HEAD version
+patch         - pick hunks and update selectively
+diff	      - view diff between HEAD and index
+add untracked - add contents of untracked files to the staged set of changes
+EOF
+}
+
+sub main_loop {
+	my @cmd = ([ 'status', \&status_cmd, ],
+		   [ 'update', \&update_cmd, ],
+		   [ 'revert', \&revert_cmd, ],
+		   [ 'add untracked', \&add_untracked_cmd, ],
+		   [ 'patch', \&patch_update_cmd, ],
+		   [ 'diff', \&diff_cmd, ],
+		   [ 'quit', \&quit_cmd, ],
+		   [ 'help', \&help_cmd, ],
+	);
+	while (1) {
+		my ($it) = list_and_choose({ PROMPT => 'What now',
+					     SINGLETON => 1,
+					     LIST_FLAT => 4,
+					     HEADER => '*** Commands ***',
+					     IMMEDIATE => 1 }, @cmd);
+		if ($it) {
+			eval {
+				$it->[1]->();
+			};
+			if ($@) {
+				print "$@";
+			}
+		}
+	}
+}
+
+my @z;
+
+refresh();
+status_cmd();
+main_loop();