Fixes for github deploy (#1774)

This addresses some long-standing comments in #1458 (comment)

We should also adopt Gatsby, create-react-app, or something similar designed for static sites, to eliminate the unnecessary runtime dependency on Next.js while also letting someone else maintain our front-end tooling. :-D These alternative tools might work just fine in subdirectories without config, and we might be able to leave Jekyll turned on (though we don’t need it). However these git-related changes are orthogonal.

- Don’t check out master, making it possible to deploy the currently checked-out commit
- Disable Jekyll which we don’t need. This allows _next folders to be deployed, and the related URL rewriting to be removed.
- Completely empty the deploy branch’s index before deployment. This prevents errors from broken symlinks, while preserving the commit history in the deploy branch.
- Do the deployment work in a git working tree. This requires Git 2.18 but makes it possible to do the above very safely.

Makefile

@@ -1,14 +1,18 @@
 SHELL:=/bin/bash
 
+DEPLOY_TEMP=${TMPDIR}shields-deploy
+
 all: website favicon test
 
 favicon:
+	# This isn't working right now. See https://github.com/badges/shields/issues/1788
 	node lib/badge-cli.js '' '' '#bada55' .png > favicon.png
 
 website:
 	LONG_CACHE=false npm run build
 
-deploy: website deploy-s0 deploy-s1 deploy-s2 deploy-gh-pages
+# `website` is needed for the server deploys.
+deploy: website deploy-s0 deploy-s1 deploy-s2 deploy-gh-pages deploy-gh-pages-clean
 
 deploy-s0:
 	# Ship a copy of the front end to each server for debugging.
@@ -34,17 +38,26 @@ deploy-s2:
 	git checkout master
 
 deploy-gh-pages:
-	(LONG_CACHE=true BASE_URL=https://img.shields.io npm run build && \
-	git checkout -B gh-pages master && \
-	cp build/index.html index.html && \
-	cp -r build/_next next && \
-	pushd next/*/page && mv {_,}error && popd && \
-	sed -i 's,/_next/,./next/,g' index.html $$(find next -type f) && \
-	sed -i 's,_error,error,g' index.html $$(find next -type f) && \
-	git add -f build index.html next && \
-	git commit -m '[DEPLOY] Build index.html' && \
-	git push -f origin gh-pages:gh-pages) || git checkout master
-	git checkout master
+	rm -rf ${DEPLOY_TEMP}
+	git worktree prune
+	LONG_CACHE=true \
+		BASE_URL=https://img.shields.io \
+		NEXT_ASSET_PREFIX=https://shields.io \
+		npm run build
+	git worktree add -B gh-pages ${DEPLOY_TEMP}
+	git -C ${DEPLOY_TEMP} ls-files | xargs git -C ${DEPLOY_TEMP} rm
+	git -C ${DEPLOY_TEMP} commit -m '[DEPLOY] Completely clean the index'
+	cp -r build/* ${DEPLOY_TEMP}
+	cp favicon.png ${DEPLOY_TEMP}
+	echo shields.io > ${DEPLOY_TEMP}/CNAME
+	touch ${DEPLOY_TEMP}/.nojekyll
+	git -C ${DEPLOY_TEMP} add .
+	git -C ${DEPLOY_TEMP} commit -m '[DEPLOY] Add built site'
+	git push -f origin gh-pages
+
+deploy-gh-pages-clean:
+	rm -rf $DEPLOY_TEMP
+	git worktree prune
 
 deploy-heroku:
 	git add -f Verdana.ttf private/secret.json build/

next.config.js

@@ -1,6 +1,7 @@
 const envFlag = require('node-env-flag');
 const webpack = require('webpack');
 const shouldAnalyze = envFlag(process.env.ANALYZE);
+const assetPrefix = process.env.NEXT_ASSET_PREFIX;
 
 module.exports = {
   webpack: config => {
@@ -22,9 +23,19 @@ module.exports = {
       loader: 'json-loader',
     });
 
+    if (assetPrefix) {
+      config.output.publicPath = `${assetPrefix}/${config.output.publicPath}`;
+    }
+
     return config;
   },
   exportPathMap: () => ({
     '/': { page: '/' },
   }),
 };
+
+// Avoid setting an `undefined` value. This causes
+// `TypeError: Cannot read property 'replace' of undefined` at build time.
+if (assetPrefix) {
+  module.exports.assetPrefix = assetPrefix;
+}