downgrade git error to a warning, and skip UX check in CI

Author: lolbinarycat

src/bootstrap/src/core/sanity.rs

@@ -382,7 +382,13 @@ $ pacman -R cmake && pacman -S mingw-w64-x86_64-cmake
  cmd_finder.must_have(s);
 }
 
-warn_old_master_branch(&build.config.git_config(),&build.config.src)
-.map_err(|e| e.to_string())
-.unwrap();
+// this warning is useless in CI,
+// and CI probably won't have the right branches anyway.
+if !build_helper::ci::CiEnv::is_ci(){
+ifletErr(e) = warn_old_master_branch(&build.config.git_config(),&build.config.src)
+.map_err(|e| e.to_string())
+{
+eprintln!("unable to check if upstream branch is old: {e}");
+}
+}
 }