rwt copy fix for Windows

Fixes redwoodjs#679

CONTRIBUTING.md

@@ -40,6 +40,8 @@ We offer two workflows for making this possible: "copy and watch", which has som
 
 ### Copy and Watch
 
+> Are you on Windows? If so, you most likely first have to [install rsync](https://tlundberg.com/blog/2020-06-15/installing-rsync-on-windows/). Also, unfortunately you can't use "copy and watch". You'll have to manually run `yarn rwt cp ../path/to/redwood` when you've made changes to the Redwood Framework (this is tracked in [issue #701](https://github.com/redwoodjs/redwood/issues/701)).
+
 First, build-and-watch files in the Redwood Framework for changes:
 
 ```terminal
@@ -52,7 +54,7 @@ create-redwood-app: $ nodemon --ignore dist --exec 'yarn build'
 @redwoodjs/eslint-plugin-redwood: $ nodemon --ignore dist --exec 'yarn build'
 ```
 
-Then, watch-and-copy those changes into your Redwood App or example app (here, [example-invoice](https://github.com/redwoodjs/example-invoice)):
+Then, copy-and-watch those changes into your Redwood App or example app (here, [example-invoice](https://github.com/redwoodjs/example-invoice)):
 
 ```terminal
 cd example-invoice

packages/cli/src/redwood-tools.js

@@ -66,6 +66,16 @@ export const fixProjectBinaries = (PROJECT_PATH) => {
 
 export const copyFiles = async (src, dest) => {
   // TODO: Figure out if we need to only run based on certain events.
+
+  if (process.platform === 'win32') {
+    // rsync doesn't do Windows paths, so we need to change them to posix paths
+    const srcDrive = src[0].toLowerCase()
+    const destDrive = dest[0].toLowerCase()
+
+    src = `/${srcDrive}/${src.substring(3).replace(/\\/g, '/')}`
+    dest = `/${destDrive}/${dest.substring(3).replace(/\\/g, '/')}`
+  }
+
   await execa('rsync', ['-rtvu --delete', `'${src}'`, `'${dest}'`], {
     shell: true,
     stdio: 'inherit',