style: add gulp task to only format changed files

gulpfile.js

@@ -29,6 +29,9 @@ function loadTask(fileName, taskName) {
 
 gulp.task('format:enforce', loadTask('format', 'enforce'));
 gulp.task('format', loadTask('format', 'format'));
+gulp.task('format:untracked', loadTask('format', 'format-untracked'));
+gulp.task('format:diff', loadTask('format', 'format-diff'));
+gulp.task('format:changed', ['format:untracked', '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']);

package.json

@@ -89,6 +89,8 @@
     "gulp-clang-format": "1.0.23",
     "gulp-connect": "5.0.0",
     "gulp-conventional-changelog": "^2.0.3",
+    "gulp-filter": "^5.1.0",
+    "gulp-git": "^2.7.0",
     "gulp-tslint": "8.1.2",
     "hammerjs": "2.0.8",
     "husky": "^0.14.3",

tools/gulp-tasks/format.js

@@ -29,6 +29,59 @@ const srcsToFmt = [
   '!tools/ts-api-guardian/test/fixtures/**',
 ];
 
+/**
+ * Gulp stream that wraps the gulp-git status,
+ * only returns untracked files, and converts
+ * the stdout into a stream of files.
+ */
+function gulpStatus() {
+  const Vinyl = require('vinyl');
+  const path = require('path');
+  const gulpGit = require('gulp-git');
+  const through = require('through2');
+  const srcStream = through.obj();
+
+  const opt = {cwd: process.cwd()};
+
+  // https://git-scm.com/docs/git-status#_short_format
+  const RE_STATUS = /((\s\w)|(\w+)|\?{0,2})\s([\w\+\-\/\\\.]+)(\s->\s)?([\w\+\-\/\\\.]+)*\n{0,1}/gm;
+
+  gulpGit.status({args: '--porcelain', quiet: true}, function(err, stdout) {
+    if (err) return srcStream.emit('error', err);
+
+    const data = stdout.toString();
+    let currentMatch;
+
+    while ((currentMatch = RE_STATUS.exec(data)) !== null) {
+      // status
+      const status = currentMatch[1].trim().toLowerCase();
+
+      // We only care about untracked files and renamed files
+      if (!new RegExp(/r|\?/i).test(status)) {
+        continue;
+      }
+
+      // file path
+      const currentFilePath = currentMatch[4];
+
+      // new file path in case its been moved
+      const newFilePath = currentMatch[6];
+      const filePath = newFilePath || currentFilePath;
+
+      srcStream.write(new Vinyl({
+        path: path.resolve(opt.cwd, filePath),
+        cwd: opt.cwd,
+      }));
+
+      RE_STATUS.lastIndex++;
+    }
+
+    srcStream.end();
+  });
+
+  return srcStream;
+}
+
 module.exports = {
   // Check source code for formatting errors (clang-format)
   enforce: (gulp) => () => {
@@ -45,5 +98,35 @@ module.exports = {
     return gulp.src(srcsToFmt, {base: '.'})
         .pipe(format.format('file', clangFormat))
         .pipe(gulp.dest('.'));
+  },
+
+  // Format only the untracked source code files with clang-format (see .clang-format)
+  'format-untracked': (gulp) => () => {
+    const format = require('gulp-clang-format');
+    const clangFormat = require('clang-format');
+    const gulpFilter = require('gulp-filter');
+
+    return gulpStatus()
+        .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('.'));
   }
 };