The unauthenticated git protocol on port 9418 is no longer supported.

git commond:git clone -b 8.2.6 git://github.com/ros2/rviz.git
Cloning into 'rviz'...
fatal: remote error: 
  The unauthenticated git protocol on port 9418 is no longer supported.
Please see https://github.blog/2021-09-01-improving-git-protocol-security-github/ for more information.
git commond:git clone -b 1.1.3 git://github.com/ros2/spdlog_vendor.git
 

解决办法：

git config --global url."https://".insteadOf git://