epm: add some nix support

bin/epm-addrepo

@@ -496,6 +496,9 @@ case $PMTYPE in
     winget)
         sudocmd winget source add "$repo"
         ;;
+    nix)
+        sudocmd nix-channel --add "$repo"
+        ;;
     termux-pkg)
         sudocmd pkg install "$repo"
         ;;

bin/epm-install

@@ -173,6 +173,10 @@ epm_install_names()
         xbps)
             sudocmd xbps-install $@
             return ;;
+        nix)
+            info "When you ask Nix to install a package, it will first try to get it in pre-compiled form from a binary cache. By default, Nix will use the binary cache https://cache.nixos.org; it contains binaries for most packages in Nixpkgs. Only if no binary is available in the binary cache, Nix will build the package from source."
+            sudocmd nix-env -iA $@
+            return ;;
         appget|winget)
             sudocmd $PMTYPE install $@
             return ;;

bin/epm-list_available

@@ -111,6 +111,9 @@ case $PMTYPE in
     apk)
         CMD="apk list --available"
         ;;
+    nix)
+        CMD="nix-env -qaP"
+        ;;
     appget)
         CMD="appget search"
         ;;

bin/epm-packages

@@ -149,6 +149,9 @@ case $PMTYPE in
     apk)
         CMD="apk list --installed"
         ;;
+    nix)
+        CMD="nix-env -q"
+        ;;
     tce)
         CMD="ls -1 /usr/local/tce.installed"
         ;;

bin/epm-update

@@ -113,6 +113,9 @@ case $PMTYPE in
     apk)
         sudocmd apk update
         ;;
+    nix)
+        sudocmd nix-channel --update
+        ;;
     pkgsrc)
         # portsnap extract for the first time?
         sudocmd portsnap fetch update

bin/epm-upgrade

@@ -178,6 +178,9 @@ epm_upgrade()
     xbps)
         CMD="xbps-install -Su"
         ;;
+    nix)
+        CMD="nix-env -u $dryrun"
+        ;;
     termux-pkg)
         CMD="pkg upgrade"
         ;;