I want to install the latest version of a package using spack. In the spack manual of the corresponding package, there is the heading Versions: master,...
To which version of the package does master refer to?
It will refer to the git master branch tip commit at the moment that you are invoking spack.
This however it is not a good idea since this means that the commit (version) can change at anytime and many project do not ensure that the state in the master branch to be stable.
I recommend you to simply use the preferred version of a package which is chosen by default when you type spack install <package>