Extract npm deps hash calculation to a separate command

default.nix

@@ -65,7 +65,7 @@ let
     CGO_ENABLED = 0;
     ldflags = "-s -w -X gopkg.c3c.cz/cv/app/server/internal/version.Tag=${version} -X gopkg.c3c.cz/cv/app/server/internal/version.Commit=${rev} -X gopkg.c3c.cz/cv/app/server/internal/version.commitTime=${commitTime} -X gopkg.c3c.cz/cv/app/server/internal/version.repoUrl=${repoUrl}";
     subPackages = [ "app/server" ];
-    vendorSha256 = "sha256-BkwXD8n62+p639vTLwXpCiY8cqYtCjWxaa5tuw78u5g=";
+    vendorSha256 = "sha256-44xcyVk5KcurQLkVJv1MeAj+Pfcu53664pvVgHdyv3E=";
     overrideModAttrs = (_: {
       impureEnvVars = pkgs.lib.fetchers.proxyImpureEnvVars ++ [ "GIT_PROXY_COMMAND" "SOCKS_SERVER" "GOPROXY" ];
     });
@@ -117,6 +117,20 @@ in
           npm --prefix app/frontend run fix
         '';
       }
+      {
+        name = "update-npm-deps-hash";
+        help = "Calculates and updates the npmDepsHash in default.nix";
+        command = ''
+          echo "Calculating npm deps"
+          # STDERR is poluted by the installed nodules, silencing
+          HASH=''$(prefetch-npm-deps ''$PRJ_ROOT/app/frontend/package-lock.json 2> /dev/null)
+          [[ ''$HASH = sha256* ]] && echo "Hash is ''$HASH"
+          [[ ''$HASH != sha256* ]] && echo "Failed" && exit 137
+
+          # Replace the first occurence of npmDepsHash with the new calculated hash in this file
+          sed -i "0,/npmDepsHash =/{s@npmDepsHash = .*@npmDepsHash = \"''$HASH\";@}" ''$PRJ_ROOT/default.nix
+        '';
+      }
       {
         name = "pre-commit";
         help = "Format and fix found issues";
@@ -125,14 +139,7 @@ in
           golangci-lint run --sort-results --out-format tab --fix
           npm --prefix ''$PRJ_ROOT/app/frontend run fix
 
-          echo "Calculating npm deps"
+          update-npm-deps-hash
-          HASH=''$(prefetch-npm-deps ''$PRJ_ROOT/app/frontend/package-lock.json 2> /dev/null)
-          [[ ''$HASH = sha256* ]] && echo "Hash is ''$HASH"
-          [[ ''$HASH != sha256* ]] && echo "Failed" && exit 137
-
-          # Replace the first occurence of npmDepsHash with the new calculated hash in this file
-          sed -i "0,/npmDepsHash =/{s@npmDepsHash = .*@npmDepsHash = \"''$HASH\";@}" ''$PRJ_ROOT/default.nix
-
         '';
       }
       {