Set version automatically

Convert the check script to a script that sets the version to match
whatever Riot is being packaged.

Add a README because the two ways of interacting with versions are
starting to get complex to reason about.

Also add a docker build script.

scripts/check-webapp.js

@@ -1,15 +0,0 @@
-#!/usr/bin/env node
-
-const fs = require('fs').promises;
-
-async function main() {
-    try {
-        const webappDir = await fs.stat('webapp.asar');
-        return 0;
-    } catch (e) {
-        console.log("No 'webapp.asar' found. Run 'yarn run fetch'");
-        return 1;
-    }
-}
-
-main().then((ret) => process.exit(ret));

scripts/dockerbuild.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+# Taken from https://www.electron.build/multi-platform-build#docker
+docker run --rm -ti \
+ --env-file <(env | grep -iE 'DEBUG|NODE_|ELECTRON_|YARN_|NPM_|CI|CIRCLE|TRAVIS_TAG|TRAVIS|TRAVIS_REPO_|TRAVIS_BUILD_|TRAVIS_BRANCH|TRAVIS_PULL_REQUEST_|APPVEYOR_|CSC_|GH_|GITHUB_|BT_|AWS_|STRIP|BUILD_') \
+ --env ELECTRON_CACHE="/root/.cache/electron" \
+ --env ELECTRON_BUILDER_CACHE="/root/.cache/electron-builder" \
+ -v ${PWD}:/project \
+ -v ${PWD##*/}-node-modules:/project/node_modules \
+ -v ~/.cache/electron:/root/.cache/electron \
+ -v ~/.cache/electron-builder:/root/.cache/electron-builder \
+ electronuserland/builder yarn run build

scripts/set-version.js

@@ -0,0 +1,39 @@
+#!/usr/bin/env node
+
+/*
+ * Checks for the pre3sence of a webapp, inspects its version and sets the
+ * version metadata of the package to match.
+ */
+
+const fs = require('fs').promises;
+const asar = require('asar');
+const child_process = require('child_process');
+
+async function main() {
+    try {
+        const webappDir = await fs.stat('webapp.asar');
+    } catch (e) {
+        console.log("No 'webapp.asar' found. Run 'yarn run fetch'");
+        return 1;
+    }
+
+    const ver = asar.extractFile('webapp.asar', 'version').toString().trim();
+    await new Promise((resolve, reject) => {
+        child_process.execFile('yarn', [
+            'version',
+            '-s',
+            '--no-git-tag-version', // This also means "don't commit to git" as it turns out
+            '--new-version',
+            ver,
+        ], (err) => {
+            if (err) {
+                reject(err);
+            } else {
+                resolve();
+            }
+        });
+    });
+    console.log("Version set to " + ver);
+}
+
+main().then((ret) => process.exit(ret));