include git-rev meta tag in dynamically-generated webpages.

app.js

@@ -15,6 +15,7 @@ var WATCH_DELAY = 300;
 
 var indexStatic;
 var router;
+var pageMeta = {};
 var app = express();
 var webpackCompiler = webpack(webpackConfig);
 
@@ -42,7 +43,9 @@ app.use(function(req, res, next) {
   if (!router.match(req.url)) {
     return next('route');
   }
-  indexStatic.generate(req.url, {}, function(err, html) {
+  indexStatic.generate(req.url, {
+    meta: pageMeta
+  }, function(err, html) {
     if (err) {
       return next(err);
     }
@@ -61,6 +64,9 @@ if (!module.parent) {
       'have recently been run with NODE_ENV="production". If this is not',
       'the case, some or all static assets may be out of date.'
     ].join('\n'));
+    pageMeta['git-rev'] = fs.readFileSync(gulpfile.GIT_REV_FILE, 'utf-8');
+    console.log('This server is based on git commit ' +
+                pageMeta['git-rev'] + '.');
     indexStaticWatcher.build(function(err, newIndexStatic) {
       if (err) {
         throw err;
@@ -73,6 +79,10 @@ if (!module.parent) {
   } else {
     require('./lib/developer-help')();
 
+    try {
+      pageMeta['git-rev'] = gulpfile.getGitRev();
+    } catch (e) {}
+
     indexStaticWatcher.watch(WATCH_DELAY, function(newIndexStatic) {
       updateIndexStatic(newIndexStatic);
       console.log('Rebuilt server-side bundle.');

gulpfile.js

@@ -1,5 +1,6 @@
 var path = require('path');
 var PassThrough = require('stream').PassThrough;
+var execSync = require('child_process').execSync;
 var _ = require('underscore');
 var gulp = require('gulp');
 var gulpif = require('gulp-if');
@@ -47,6 +48,7 @@ var LINT_DIRS = [
 ];
 
 var LESS_FILES = './less/**/*.less';
+var GIT_REV_FILE = path.join(__dirname, 'dist', 'git-rev.txt');
 
 function onError(err) {
   gutil.log(gutil.colors.red(err));
@@ -60,16 +62,19 @@ function handleError() {
   });
 }
 
+function getGitRev() {
+  return execSync('git rev-parse HEAD', {
+    cwd: __dirname,
+    encoding: 'utf8'
+  }).slice(0, 40);
+}
+
 function createIndexFileStream() {
   var stream = new PassThrough({ objectMode: true });
   var meta = {};
-  var execSync = require('child_process').execSync;
 
   try {
-    meta['git-rev'] = execSync('git rev-parse HEAD', {
-      cwd: __dirname,
-      encoding: 'utf8'
-    }).slice(0, 40);
+    meta['git-rev'] = getGitRev();
   } catch (e) {}
 
   indexStaticWatcher.build(function(err, indexStatic) {
@@ -307,9 +312,13 @@ gulp.task('s3', BUILD_TASKS, function() {
 });
 
 if (process.env.NODE_ENV === 'production') {
-  gulp.task('postinstall', MINIMAL_BUILD_TASKS);
+  gulp.task('postinstall', MINIMAL_BUILD_TASKS, function() {
+    require('fs').writeFileSync(GIT_REV_FILE, getGitRev());
+  });
 } else {
   gulp.task('postinstall');
 }
 
 module.exports.LESS_FILES = LESS_FILES;
+module.exports.GIT_REV_FILE = GIT_REV_FILE;
+module.exports.getGitRev = getGitRev;