Going through old backup files, I came across an old server (beta 1.8.1) as well as the client jar, mcpatcher, and the old texture pack that I used to use. I thought it would be fun to play around in the old world and was able to connect (by putting the server in offline mode) and wander around – but only by using the vanilla texturepack.

I was able to run mcpatcher to patch the downloaded b1.8.1.jar that is downloaded by the modern Minecraft Launcher, but as soon as I attempted to use the Launcher to run my patched jar, it noticed that the file was modified, erased it, and downloaded a non-patched version, which precludes me from using my texturepack.

Please provide an advanced setting that turns off checksum checking of the jar so that it will run my patched jar and let me - and others - use their old texture packs on their old servers.