style: add combined task to format from git diff and status commands (angular#24969)

PR Close angular#24969

Author: brandonroberts

gulpfile.js

@@ -29,7 +29,9 @@ function loadTask(fileName, taskName) {
 
 gulp.task('format:enforce', loadTask('format', 'enforce'));
 gulp.task('format', loadTask('format', 'format'));
-gulp.task('format:changed', loadTask('format', 'format-changed'));
+gulp.task('format:changes', loadTask('format', 'format-changes'));
+gulp.task('format:diff', loadTask('format', 'format-diff'));
+gulp.task('format:changed', ['format:changes', 'format:diff']);
 gulp.task('build.sh', loadTask('build', 'all'));
 gulp.task('build.sh:no-bundle', loadTask('build', 'no-bundle'));
 gulp.task('lint', ['format:enforce', 'validate-commit-messages', 'tslint']);

tools/gulp-tasks/format.js

@@ -103,7 +103,7 @@ module.exports = {
   },
 
   // Format only the changed source code files with clang-format (see .clang-format)
-  'format-changed': (gulp) => () => {
+  'format-changes': (gulp) => () => {
     const format = require('gulp-clang-format');
     const clangFormat = require('clang-format');
     const gulpFilter = require('gulp-filter');
@@ -112,5 +112,23 @@ module.exports = {
         .pipe(gulpFilter(srcsToFmt))
         .pipe(format.format('file', clangFormat))
         .pipe(gulp.dest('.'));
+  },
+
+  // Format only the changed source code files diffed from the provided branch with clang-format
+  // (see .clang-format)
+  'format-diff': (gulp) => () => {
+    const format = require('gulp-clang-format');
+    const clangFormat = require('clang-format');
+    const gulpFilter = require('gulp-filter');
+    const minimist = require('minimist');
+    const gulpGit = require('gulp-git');
+
+    const args = minimist(process.argv.slice(2));
+    const branch = args.branch || 'master';
+
+    return gulpGit.diff(branch, {log: false})
+        .pipe(gulpFilter(srcsToFmt))
+        .pipe(format.format('file', clangFormat))
+        .pipe(gulp.dest('.'));
   }
 };