use static version for session checking, show latest changeset for git version instead of head date

include/functions.php

@@ -659,7 +659,7 @@
 				@session_start();
 
 				$_SESSION["uid"] = $user_id;
-				$_SESSION["version"] = VERSION;
+				$_SESSION["version"] = VERSION_STATIC;
 
 				$result = db_query("SELECT login,access_level,pwd_hash FROM ttrss_users
 					WHERE id = '$user_id'");

include/sessions.php

@@ -39,7 +39,7 @@
 	function validate_session() {
 		if (SINGLE_USER_MODE) return true;
 
-		if (VERSION != $_SESSION["version"]) return false;
+		if (VERSION_STATIC != $_SESSION["version"]) return false;
 
 		$check_ip = $_SESSION['ip_address'];
 

include/version.php

@@ -7,7 +7,7 @@
 
 		if (is_dir("$root_dir/.git") && file_exists("$root_dir/.git/ORIG_HEAD")) {
 
-			$suffix = date("Ymd", filemtime("$root_dir/.git/ORIG_HEAD"));
+			$suffix = substr(trim(file_get_contents("$root_dir/.git/ORIG_HEAD")), 0, 7);
 
 			return VERSION_STATIC . ".$suffix";
 		} else {