I want to suggest a new step

Which tool is this about? Where is its repository?

The tool is ZVM. It's the Zig Version Manager.

Which operating systems are supported by this tool?

• Windows
• Linux
• MacOS
• FreeBSD
• NetBSD
• Plan9
• Solaris

What should Topgrade do to figure out if the tool needs to be invoked?

It depends on what you're most comfortable with. ZVM comes with its own self-upgrade functionality. Just running that will automatically upgrade ZVM to the latest version, or print a nice message to stdout if the latest version is already installed.

If you'd rather grab ZVM manually, the releases are all hosted on GitHub and organized by zvm-${os}-${arch}. The bundle just needs to be unpacked in $ZVM_INSTALL or ~/.zvm/self if the former is not set. Add that directory and ~/$(ZVM_INSTALL)/../bin to path as well.

This is the equivalent bash.

echo "# ZVM" >> $HOME/.profile
echo export ZVM_INSTALL="$HOME/.zvm/self" >> $HOME/.profile
echo export PATH="$PATH:$HOME/.zvm/bin" >> $HOME/.profile
echo export PATH="$PATH:$ZVM_INSTALL/" >> $HOME/.profile

Which exact commands should Topgrade run?

zvm upgrade

More information

ZVM comes with one-line install scripts for Bash and Windows. The Bash Script does not edit environment variables, but that's just because I'm not comfortable with Bash enough to edit user's configs. Following the install script will show you step-by-step how to install and configure ZVM.