Rebuild task in gulp.

gulpfile.js

@@ -770,3 +770,51 @@ gulp.task('release', gulp.series(['build', 'typings', function() {
 
 // The default task builds Blockly.
 gulp.task('default', gulp.series(['build']));
+
+// Stash current state, check out develop, and sync with google/blockly.
+gulp.task('syncDevelop', function(done) {
+  execSync('git stash save -m "Stash for sync"', { stdio: 'inherit' });
+  execSync('git checkout develop', { stdio: 'inherit' });
+  execSync('git pull https://github.com/google/blockly.git develop',
+      { stdio: 'inherit' });
+  execSync('git push origin develop', { stdio: 'inherit' });
+  done();
+});
+
+// Helper function: get a name for a rebuild branch. Format: rebuild_mm_dd_yyyy.
+function getRebuildBranchName() {
+  var date = new Date();
+  var mm = date.getMonth() + 1; // Month, 0-11
+  var dd = date.getDate(); // Day of the month, 1-31
+  var yyyy = date.getFullYear();
+  return 'rebuild_' + mm + '_' + dd + '_' + yyyy;
+}
+
+// Stash and make a new branch for a rebuild.
+gulp.task('make-rebuild-branch', function(done) {
+  execSync('git stash save -m "Stash for rebuild"', { stdio: 'inherit' });
+  var branchName = getRebuildBranchName();
+  console.log('make-rebuild-branch: creating branch ' + branchName);
+  execSync('git checkout -b ' + branchName, { stdio: 'inherit' });
+  done();
+});
+
+// Commit and push the current rebuild branch.
+gulp.task('push-rebuild-branch', function(done) {
+  console.log('push-rebuild-branch: committing rebuild');
+  execSync('git commit -am "Rebuild"', { stdio: 'inherit' });
+  var branchName = getRebuildBranchName();
+  execSync('git push origin ' + branchName, { stdio: 'inherit' });
+  console.log('Branch ' + branchName + ' pushed to GitHub.');
+  console.log('Next step: create a pull request against develop.');
+  done();
+});
+
+// Recompile and push to origin.
+gulp.task('recompile', gulp.series[
+    'syncDevelop',
+    'make-rebuild-branch'
+    'build',
+    'push-rebuild-branch'
+  ]
+);