scripts/deploy: allow --deriv to be either a .drv or a store path

scripts/deploy

@@ -19,7 +19,7 @@ usage() {
   echo "- --variant light|min|''|all  (default: '')"
   echo "- --wireguard always|never|opportunistic: deploy over wireguard"
   echo "- --ip <address>: deploy to the specific IP address"
-  echo "- --deriv /nix/store/...: prebuilt store path to deploy instead of (re-)building the default target"
+  echo "- --deriv /nix/store/...: prebuilt store path (or .drv to realize) to deploy instead of (re-)building the default target"
   echo ""
   echo "common idioms:"
   echo "- deploy all: deploy all hosts, sequentially"
@@ -197,14 +197,19 @@ deployOneHost() {
 
   local timeout=$(timeoutFor "$variant")
 
+  # storePath is allowed to be either a realized derivation,
+  # or the path to a .drv file itself
   local myStorePath="$storePath"
   if [ -z "$myStorePath" ]; then
     # `nix-build -A foo` evals and then realizes foo, but it never unloads the memory used to eval foo.
     # my exprs are heavyweight, we need that memory for building, so do the evals separately from the realizations:
     info "evaluating $host$variant..."
-    local drvPath=$(nix eval --raw -f . "hosts.$host$variant.toplevel.drvPath")
+    myStorePath=$(nix eval --raw -f . "hosts.$host$variant.toplevel.drvPath")
+  fi
+
+  if [[ "$myStorePath" == *.drv ]]; then
     info "building $host$variant ($drvPath)"
-    myStorePath=$(destructive nix-store --realize "$drvPath" "${nixArgs[@]}")
+    myStorePath=$(destructive nix-store --realize "$myStorePath" "${nixArgs[@]}")
     if [ -z "$myStorePath" ]; then
       return 1
     fi