Merge branch 'jk/empty-archive' into maint

"git archive" reports a failure when asked to create an archive out
of an empty tree.  It would be more intuitive to give an empty
archive back in such a case.

* jk/empty-archive:
  archive: handle commits with an empty tree
  test-lib: factor out $GIT_UNZIP setup

archive.c

@@ -234,7 +234,7 @@ static void parse_pathspec_arg(const char **pathspec,
 	ar_args->pathspec = pathspec = get_pathspec("", pathspec);
 	if (pathspec) {
 		while (*pathspec) {
-			if (!path_exists(ar_args->tree, *pathspec))
+			if (**pathspec && !path_exists(ar_args->tree, *pathspec))
 				die("path not found: %s", *pathspec);
 			pathspec++;
 		}

t/t0024-crlf-archive.sh

@@ -3,12 +3,6 @@
 test_description='respect crlf in git archive'
 
 . ./test-lib.sh
-GIT_UNZIP=${GIT_UNZIP:-unzip}
-
-test_lazy_prereq UNZIP '
-	"$GIT_UNZIP" -v
-	test $? -ne 127
-'
 
 test_expect_success setup '
 

t/t5003-archive-zip.sh

@@ -3,15 +3,9 @@
 test_description='git archive --format=zip test'
 
 . ./test-lib.sh
-GIT_UNZIP=${GIT_UNZIP:-unzip}
 
 SUBSTFORMAT=%H%n
 
-test_lazy_prereq UNZIP '
-	"$GIT_UNZIP" -v
-	test $? -ne 127
-'
-
 test_lazy_prereq UNZIP_SYMLINKS '
 	(
 		mkdir unzip-symlinks &&

t/t5004-archive-corner-cases.sh

@@ -0,0 +1,102 @@
+#!/bin/sh
+
+test_description='test corner cases of git-archive'
+. ./test-lib.sh
+
+test_expect_success 'create commit with empty tree' '
+	git commit --allow-empty -m foo
+'
+
+# Make a dir and clean it up afterwards
+make_dir() {
+	mkdir "$1" &&
+	test_when_finished "rm -rf '$1'"
+}
+
+# Check that the dir given in "$1" contains exactly the
+# set of paths given as arguments.
+check_dir() {
+	dir=$1; shift
+	{
+		echo "$dir" &&
+		for i in "$@"; do
+			echo "$dir/$i"
+		done
+	} | sort >expect &&
+	find "$dir" -print | sort >actual &&
+	test_cmp expect actual
+}
+
+test_expect_success 'tar archive of empty tree is empty' '
+	git archive --format=tar HEAD >empty.tar &&
+	make_dir extract &&
+	"$TAR" xf empty.tar -C extract &&
+	check_dir extract
+'
+
+test_expect_success 'tar archive of empty tree with prefix' '
+	git archive --format=tar --prefix=foo/ HEAD >prefix.tar &&
+	make_dir extract &&
+	"$TAR" xf prefix.tar -C extract &&
+	check_dir extract foo
+'
+
+test_expect_success UNZIP 'zip archive of empty tree is empty' '
+	# Detect the exit code produced when our particular flavor of unzip
+	# sees an empty archive. Infozip will generate a warning and exit with
+	# code 1. But in the name of sanity, we do not expect other unzip
+	# implementations to do the same thing (it would be perfectly
+	# reasonable to exit 0, for example).
+	#
+	# This makes our test less rigorous on some platforms (unzip may not
+	# handle the empty repo at all, making our later check of its exit code
+	# a no-op). But we cannot do anything reasonable except skip the test
+	# on such platforms anyway, and this is the moral equivalent.
+	"$GIT_UNZIP" "$TEST_DIRECTORY"/t5004/empty.zip
+	expect_code=$?
+
+	git archive --format=zip HEAD >empty.zip &&
+	make_dir extract &&
+	(
+		cd extract &&
+		test_expect_code $expect_code "$GIT_UNZIP" ../empty.zip
+	) &&
+	check_dir extract
+'
+
+test_expect_success UNZIP 'zip archive of empty tree with prefix' '
+	# We do not have to play exit-code tricks here, because our
+	# result should not be empty; it has a directory in it.
+	git archive --format=zip --prefix=foo/ HEAD >prefix.zip &&
+	make_dir extract &&
+	(
+		cd extract &&
+		"$GIT_UNZIP" ../prefix.zip
+	) &&
+	check_dir extract foo
+'
+
+test_expect_success 'archive complains about pathspec on empty tree' '
+	test_must_fail git archive --format=tar HEAD -- foo >/dev/null
+'
+
+test_expect_success 'create a commit with an empty subtree' '
+	empty_tree=$(git hash-object -t tree /dev/null) &&
+	root_tree=$(printf "040000 tree $empty_tree\tsub\n" | git mktree)
+'
+
+test_expect_success 'archive empty subtree with no pathspec' '
+	git archive --format=tar $root_tree >subtree-all.tar &&
+	make_dir extract &&
+	"$TAR" xf subtree-all.tar -C extract &&
+	check_dir extract sub
+'
+
+test_expect_success 'archive empty subtree by direct pathspec' '
+	git archive --format=tar $root_tree -- sub >subtree-path.tar &&
+	make_dir extract &&
+	"$TAR" xf subtree-path.tar -C extract &&
+	check_dir extract sub
+'
+
+test_done

t/test-lib.sh

@@ -760,3 +760,9 @@ test_lazy_prereq AUTOIDENT '
 # When the tests are run as root, permission tests will report that
 # things are writable when they shouldn't be.
 test -w / || test_set_prereq SANITY
+
+GIT_UNZIP=${GIT_UNZIP:-unzip}
+test_lazy_prereq UNZIP '
+	"$GIT_UNZIP" -v
+	test $? -ne 127
+'