Problem

nix-env handles special characters in package names specially, e.g. +.

There are some package names in nixpkgs with "special characters", e.g. + in it.
Using these package names with nix-env directly does not work; but a backslash must be added before the +. That is unintuitive.

Solution

Fix nix-env (and maybe also other parts of Nix), so special characters in package names can be used directly.

Example

• Package: gtk+3-3.24.13
• nix-env -q lists the package correctly as gtk+3-3.24.13
• nix-env -i 'gtk+3-3.24.13', nix-env -u 'gtk+3-3.24.13', nix-env -e 'gtk+3-3.24.13' all do not work.
• They only work, if gtk\+3-3.24.13 is used instead.