Merge branch 'jk/empty-tree'

* jk/empty-tree:
  add--interactive: handle initial commit better
  hard-code the empty tree object

git-add--interactive.perl

@@ -82,6 +82,19 @@ sub list_untracked {
 my $status_fmt = '%12s %12s %s';
 my $status_head = sprintf($status_fmt, 'staged', 'unstaged', 'path');
 
+{
+	my $initial;
+	sub is_initial_commit {
+		$initial = system('git rev-parse HEAD -- >/dev/null 2>&1') != 0
+			unless defined $initial;
+		return $initial;
+	}
+}
+
+sub get_empty_tree {
+	return '4b825dc642cb6eb9a060e54bf8d69288fbee4904';
+}
+
 # Returns list of hashes, contents of each of which are:
 # VALUE:	pathname
 # BINARY:	is a binary path
@@ -103,8 +116,10 @@ sub list_modified {
 		return if (!@tracked);
 	}
 
+	my $reference = is_initial_commit() ? get_empty_tree() : 'HEAD';
 	for (run_cmd_pipe(qw(git diff-index --cached
-			     --numstat --summary HEAD --), @tracked)) {
+			     --numstat --summary), $reference,
+			     '--', @tracked)) {
 		if (($add, $del, $file) =
 		    /^([-\d]+)	([-\d]+)	(.*)/) {
 			my ($change, $bin);
@@ -476,6 +491,11 @@ sub revert_cmd {
 				       HEADER => $status_head, },
 				     list_modified());
 	if (@update) {
+		if (is_initial_commit()) {
+			system(qw(git rm --cached),
+				map { $_->{VALUE} } @update);
+		}
+		else {
 			my @lines = run_cmd_pipe(qw(git ls-tree HEAD --),
 						 map { $_->{VALUE} } @update);
 			my $fh;
@@ -493,6 +513,7 @@ sub revert_cmd {
 					print "note: $_->{VALUE} is untracked now.\n";
 				}
 			}
+		}
 		refresh();
 		say_n_paths('reverted', @update);
 	}
@@ -956,7 +977,9 @@ sub diff_cmd {
 				     HEADER => $status_head, },
 				   @mods);
 	return if (!@them);
-	system(qw(git diff -p --cached HEAD --), map { $_->{VALUE} } @them);
+	my $reference = is_initial_commit() ? get_empty_tree() : 'HEAD';
+	system(qw(git diff -p --cached), $reference, '--',
+		map { $_->{VALUE} } @them);
 }
 
 sub quit_cmd {

sha1_file.c

@@ -1845,6 +1845,15 @@ static struct cached_object {
 } *cached_objects;
 static int cached_object_nr, cached_object_alloc;
 
+static struct cached_object empty_tree = {
+	/* empty tree sha1: 4b825dc642cb6eb9a060e54bf8d69288fbee4904 */
+	"\x4b\x82\x5d\xc6\x42\xcb\x6e\xb9\xa0\x60"
+	"\xe5\x4b\xf8\xd6\x92\x88\xfb\xee\x49\x04",
+	OBJ_TREE,
+	"",
+	0
+};
+
 static struct cached_object *find_cached_object(const unsigned char *sha1)
 {
 	int i;
@@ -1854,6 +1863,8 @@ static struct cached_object *find_cached_object(const unsigned char *sha1)
 		if (!hashcmp(co->sha1, sha1))
 			return co;
 	}
+	if (!hashcmp(sha1, empty_tree.sha1))
+		return &empty_tree;
 	return NULL;
 }
 

t/t3701-add-interactive.sh

@@ -0,0 +1,69 @@
+#!/bin/sh
+
+test_description='add -i basic tests'
+. ./test-lib.sh
+
+test_expect_success 'setup (initial)' '
+	echo content >file &&
+	git add file &&
+	echo more >>file &&
+	echo lines >>file
+'
+test_expect_success 'status works (initial)' '
+	git add -i </dev/null >output &&
+	grep "+1/-0 *+2/-0 file" output
+'
+cat >expected <<EOF
+new file mode 100644
+index 0000000..d95f3ad
+--- /dev/null
++++ b/file
+@@ -0,0 +1 @@
++content
+EOF
+test_expect_success 'diff works (initial)' '
+	(echo d; echo 1) | git add -i >output &&
+	sed -ne "/new file/,/content/p" <output >diff &&
+	diff -u expected diff
+'
+test_expect_success 'revert works (initial)' '
+	git add file &&
+	(echo r; echo 1) | git add -i &&
+	git ls-files >output &&
+	! grep . output
+'
+
+test_expect_success 'setup (commit)' '
+	echo baseline >file &&
+	git add file &&
+	git commit -m commit &&
+	echo content >>file &&
+	git add file &&
+	echo more >>file &&
+	echo lines >>file
+'
+test_expect_success 'status works (commit)' '
+	git add -i </dev/null >output &&
+	grep "+1/-0 *+2/-0 file" output
+'
+cat >expected <<EOF
+index 180b47c..b6f2c08 100644
+--- a/file
++++ b/file
+@@ -1 +1,2 @@
+ baseline
++content
+EOF
+test_expect_success 'diff works (commit)' '
+	(echo d; echo 1) | git add -i >output &&
+	sed -ne "/^index/,/content/p" <output >diff &&
+	diff -u expected diff
+'
+test_expect_success 'revert works (commit)' '
+	git add file &&
+	(echo r; echo 1) | git add -i &&
+	git add -i </dev/null >output &&
+	grep "unchanged *+3/-0 file" output
+'
+
+test_done