automatically produce MSI files for releases

This commit:

- Adds config for building Windows installers
- Adds an action for fetching exe files built by goreleaser
- Adds an action for building Windows installers
- Adds an action for adding MSI files to an existing GH release
- Adds MSI signing to our release flow
- Disables homebrew formula bumping for prereleases
- Allows the release asset copying action to copy windows assets

.github/actions/build-msi/index.js

@@ -0,0 +1,64 @@
+const core = require('@actions/core');
+const github = require('@actions/github');
+const exec = require('@actions/exec');
+const fs = require('fs');
+const path = require('path');
+
+process.on('unhandledRejection', function(reason, _) {
+  handleError(reason);
+});
+
+function addToPath(_path) {
+  console.log(`adding ${_path} to Path`);
+  process.env['Path'] = _path + ';' + process.env['Path'];
+}
+
+main().catch(handleError)
+
+async function main() {
+  const exePath = core.getInput('exe');
+  const version = github.context.ref.replace('refs/tags/', '');
+
+  console.log(`Building MSI for version ${version}`);
+  const wixPath = process.env['WIX'] + '\\bin';
+
+  addToPath(wixPath);
+
+  await go_msi(version, exePath);
+}
+
+async function go_msi(version, exePath) {
+  const cwd = process.cwd();
+
+  // go-msi was struggling with its default temp dir; it wanted something relative to the source dir
+  // for some reason.
+  console.log('making build path');
+  const buildPath = path.join(cwd, 'build');
+  fs.mkdirSync(buildPath);
+
+  console.log('making bin path');
+  const binPath = path.join(cwd, 'bin');
+  fs.mkdirSync(binPath);
+  console.log(`moving ${exePath} to bin/gh.exe`);
+  fs.renameSync(exePath, path.join(binPath, 'gh.exe'));
+
+  const msiPath = path.join(cwd, 'gh.msi');
+
+  try {
+    await exec.exec(
+      '"C:\\Program Files\\go-msi\\go-msi.exe"',
+      ['make',
+       '--msi', msiPath,
+       '--out', buildPath,
+       '--version', version]);
+    console.log(`build MSI at ${msiPath}`);
+    core.setOutput('msi', msiPath);
+  } catch(e) {
+    core.setFailed(e.message);
+  }
+}
+
+async function handleError(err) {
+  console.error(err);
+  core.setFailed(err.message);
+}