Merge 'update/virtual-file-system'

Update the virtualfilesystem support to specify it needs to be run from
the root of the git work tree. This enables the hook to be found even if
the current working directory is not the root of the repo (like when
running 'git diff' with Beyond Compare configured as the diff tool).

Also simplify how argv[] parameter is created to match the model
currently accepted in master.

Author: dscho

virtualfilesystem.c

@@ -32,18 +32,14 @@ static int vfs_hashmap_cmp(const void *unused_cmp_data,
 static void get_virtual_filesystem_data(struct strbuf *vfs_data)
 {
 	struct child_process cp = CHILD_PROCESS_INIT;
-	char ver[64];
-	const char *argv[3];
 	int err;
 
 	strbuf_init(vfs_data, 0);
 
-	snprintf(ver, sizeof(ver), "%d", HOOK_INTERFACE_VERSION);
-	argv[0] = core_virtualfilesystem;
-	argv[1] = ver;
-	argv[2] = NULL;
-	cp.argv = argv;
+	argv_array_push(&cp.args, core_virtualfilesystem);
+	argv_array_pushf(&cp.args, "%d", HOOK_INTERFACE_VERSION);
 	cp.use_shell = 1;
+	cp.dir = get_git_work_tree();
 
 	err = capture_command(&cp, vfs_data, 1024);
 	if (err)