diff --git a/.tangled/workflows/build.yml b/.tangled/workflows/build.yml
new file mode 100644
index 0000000..76bdb74
--- /dev/null
+++ b/.tangled/workflows/build.yml
@@ -0,0 +1,17 @@
+when:
+  - event: ["push", "manual"]
+    branch: ["main"]
+engine: "nixery"
+dependencies:
+  nixpkgs:
+    - nodejs
+    - gnumake
+    - diffutils
+    - findutils
+    - git
+    - time
+steps:
+  - name: "build newt"
+    command: "make newt3.js"
+  - name: "test"
+    command: "make test"
diff --git a/Makefile b/Makefile
index 7eea2e8..4eedb65 100644
--- a/Makefile
+++ b/Makefile
@@ -9,11 +9,8 @@ RUNJS=node
 all: newt.js
 
 
-REV=$(shell git rev-parse --short HEAD)
 src/Revision.newt: .PHONY
-	echo "module Revision\nimport Prelude\ngitRevision : String\ngitRevision = \"${REV}\"" > src/Revision.newt.new
-	cmp src/Revision.newt.new src/Revision.newt || cp src/Revision.newt.new src/Revision.newt
-	rm -f src/Revision.newt.new
+	sh ./scripts/mkrevision
 
 newt.js: ${SRCS} src/Revision.newt
 	$(RUNJS) bootstrap/newt.js src/Main.newt -o newt.js
diff --git a/scripts/mkrevision b/scripts/mkrevision
new file mode 100755
index 0000000..9671ee6
--- /dev/null
+++ b/scripts/mkrevision
@@ -0,0 +1,12 @@
+#!/bin/sh -e
+REV=$(git rev-parse --short HEAD)
+cat >> src/Revision.newt.new <<EOF
+module Revision
+
+import Prelude
+
+gitRevision : String
+gitRevision = "$REV"
+EOF
+cmp src/Revision.newt.new src/Revision.newt || cp src/Revision.newt.new src/Revision.newt
+rm -f src/Revision.newt.new