Use git_identifier instead of version_number

vm/src/sysmodule.rs

@@ -166,7 +166,7 @@ fn sys_exc_info(vm: &VirtualMachine) -> PyResult {
 fn sys_git_info(vm: &VirtualMachine) -> PyObjectRef {
     vm.ctx.new_tuple(vec![
         vm.ctx.new_str("RustPython".to_string()),
-        vm.ctx.new_str(version::get_version_number()),
+        vm.ctx.new_str(version::get_git_identifier()),
         vm.ctx.new_str(version::get_git_revision()),
     ])
 }

vm/src/version.rs

@@ -47,3 +47,14 @@ pub fn get_git_branch() -> String {
         .unwrap_or("")
         .to_string()
 }
+
+pub fn get_git_identifier() -> String {
+    let git_tag = get_git_tag();
+    let git_branch = get_git_branch();
+
+    if git_tag.is_empty() || git_tag == "undefined" {
+        git_branch
+    } else {
+        git_tag
+    }
+}