vcs-svn: More dump format sanity checks

Node-action: change is not appropriate when switching between file and
directory or adding a new file.  Current svn-fe silently accepts such
nodes and the resulting tree has missing files in the "changed when
meant to add" case.

Node-action: add requires some content (text or directory); there is
no such thing as an "intent to add" node in svn dumps.  Current svn-fe
accepts such contentless adds but produces an invalid fast-import
stream that refers to nonexistent mark :0 in response.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9010-svn-fe.sh

@@ -272,6 +272,27 @@ test_expect_success 'node without action' '
 	test_must_fail test-svn-fe inaction.dump
 '
 
+test_expect_success 'action: add node without text' '
+	cat >textless.dump <<-\EOF &&
+	SVN-fs-dump-format-version: 3
+
+	Revision-number: 1
+	Prop-content-length: 10
+	Content-length: 10
+
+	PROPS-END
+
+	Node-path: textless
+	Node-kind: file
+	Node-action: add
+	Prop-content-length: 10
+	Content-length: 10
+
+	PROPS-END
+	EOF
+	test_must_fail test-svn-fe textless.dump
+'
+
 test_expect_failure 'change file mode but keep old content' '
 	reinit_git &&
 	cat >expect <<-\EOF &&

vcs-svn/svndump.c

@@ -181,12 +181,22 @@ static void handle_node(void)
 	if (mark && type == REPO_MODE_DIR)
 		die("invalid dump: directories cannot have text attached");
 
-	if (node_ctx.action == NODEACT_CHANGE)
-		node_ctx.type = repo_modify_path(node_ctx.dst, 0, mark);
-	else if (node_ctx.action == NODEACT_ADD)
+	if (node_ctx.action == NODEACT_CHANGE) {
+		uint32_t mode = repo_modify_path(node_ctx.dst, 0, mark);
+		if (!mode)
+			die("invalid dump: path to be modified is missing");
+		if (mode == REPO_MODE_DIR && type != REPO_MODE_DIR)
+			die("invalid dump: cannot modify a directory into a file");
+		if (mode != REPO_MODE_DIR && type == REPO_MODE_DIR)
+			die("invalid dump: cannot modify a file into a directory");
+		node_ctx.type = mode;
+	} else if (node_ctx.action == NODEACT_ADD) {
+		if (!mark && type != REPO_MODE_DIR)
+			die("invalid dump: adds node without text");
 		repo_add(node_ctx.dst, type, mark);
-	else
+	} else {
 		die("invalid dump: Node-path block lacks Node-action");
+	}
 
 	if (have_props) {
 		const uint32_t old_mode = node_ctx.type;