nixpkgs: add non-default names for packages

This makes working with nix profile upgrade easier since it only matches
on the attribute names and not the flake source.

.config/nixpkgs/elvish/flake.nix

@@ -35,7 +35,7 @@
           vendorSha256 = "sha256-WXntyDbpGEXHkYgv21vN/JG/CVn6SqnMhmgXfFEQ9eM=";
         };
 
-      packages.x86_64-linux.default =
+      packages.x86_64-linux.elvish =
         with import nixpkgs {
           system = "x86_64-linux";
         };
@@ -64,5 +64,7 @@
           fi
           exec ${elvish}/bin/elvish -rc "${config}/elvish/rc.elv" "$@"
         '';
+
+      packages.x86_64-linux.default = self.packages.x86_64-linux.elvish;
     };
 }

.config/nixpkgs/neovim/flake.nix

@@ -12,7 +12,8 @@
       };
     in
     {
-      packages.x86_64-linux.default = (withPkgs "x86_64-linux").callPackage ./neovim.nix {};
-      packages.x86_64-linux.playground = (withPkgs "x86_64-linux").callPackage ./neovim.nix { withPlayground = true; };
+      packages.x86_64-linux.neovim = (withPkgs "x86_64-linux").callPackage ./neovim.nix {};
+      packages.x86_64-linux.neovim-with-playground = (withPkgs "x86_64-linux").callPackage ./neovim.nix { withPlayground = true; };
+      packages.x86_64-linux.default = self.packages.x86_64-linux.neovim;
     };
 }

.config/nixpkgs/zsh/flake.nix

@@ -3,7 +3,7 @@
 
   outputs = { self, nixpkgs }:
     {
-      packages.x86_64-linux.default =
+      packages.x86_64-linux.zsh =
         with import nixpkgs {
           system = "x86_64-linux";
         };
@@ -60,5 +60,7 @@
           echo "Could not find system zsh"
           exit 1
         '';
+
+      packages.x86_64-linux.default = self.packages.x86_64-linux.zsh;
     };
 }