dovecot: read dovecot version into nix variable
This adds a file dovecot-version.nix
which is a derivation that produces a JSON blob like this:
❯ nix-build --expr 'with import <nixpkgs> {}; callPackage ./mail-server/dovecot-version.nix {}' && cat result
/nix/store/8srvh6d7d7c4n9jj83jz3fpdn0na4986-dovecot-version
{
"major": 2,
"minor": 3,
"patch": 0
}
It can be used like this to check the current dovecot
version:
nix-repl> builtins.fromJSON (builtins.readFile (pkgs.callPackage ./dovecot-version.nix {}))
{ major = 2; minor = 2; patch = 33; }