Add dry-run option

lib/index.js

@@ -125,7 +125,8 @@ class Generator extends EventEmitter {
     this.conflicter = new Conflicter(this.env.adapter, this.options.force, {
       bail: this.options.bail,
       ignoreWhitespace: this.options.whitespace,
-      skipRegenerate: this.options.skipRegenerate
+      skipRegenerate: this.options.skipRegenerate,
+      dryRun: this.options.dryRun
     });
 
     // Mirror the adapter log method on the generator.

lib/util/conflicter.js

@@ -42,6 +42,7 @@ class Conflicter {
       this.bail = options.bail;
       this.ignoreWhitespace = options.ignoreWhitespace;
       this.skipRegenerate = options.skipRegenerate;
+      this.dryRun = options.dryRun;
     }
 
     this.force = force === true;
@@ -56,6 +57,11 @@ class Conflicter {
       this.ignoreWhitespace = true;
       this.skipRegenerate = true;
     }
+
+    if (this.dryRun) {
+      // Ignore whitespace changes with "ignoreWhitespace === true" option
+      this.skipRegenerate = true;
+    }
   }
 
   /**
@@ -210,6 +216,11 @@ class Conflicter {
         throw new ConflictError();
       }
 
+      if (this.dryRun) {
+        cb('skip');
+        return;
+      }
+
       cb('create');
       return;
     }
@@ -228,6 +239,12 @@ class Conflicter {
         throw new ConflictError();
       }
 
+      if (this.dryRun) {
+        this._printDiff(file);
+        cb('skip');
+        return;
+      }
+
       this._ask(file, cb);
     } else {
       this.adapter.log.identical(rfilepath);

test/conflicter.js

@@ -155,6 +155,75 @@ describe('Conflicter', () => {
       done();
     });
 
+    it('skip file changes with dryRun', function(done) {
+      const conflicter = new Conflicter(new TestAdapter(), false, {
+        dryRun: true
+      });
+      conflicter.collision(
+        {
+          path: path.join(__dirname, 'fixtures/file-conflict.txt'),
+          contents: `initial
+                 content
+      `
+        },
+        status => {
+          assert.equal(status, 'skip');
+          done();
+        }
+      );
+    });
+
+    it('skip new file with dryRun', function(done) {
+      const conflicter = new Conflicter(new TestAdapter(), false, {
+        dryRun: true
+      });
+      conflicter.collision(
+        {
+          path: 'file-who-does-not-exist2.js',
+          contents: ''
+        },
+        status => {
+          assert.equal(status, 'skip');
+          done();
+        }
+      );
+    });
+
+    it('skip deleted file with dryRun', function(done) {
+      const conflicter = new Conflicter(new TestAdapter(), false, {
+        dryRun: true
+      });
+      conflicter.collision(
+        {
+          path: path.join(__dirname, 'fixtures/foo.js'),
+          contents: null
+        },
+        status => {
+          assert.equal(status, 'skip');
+          done();
+        }
+      );
+    });
+
+    it('skip whitespace changes with dryRun', function(done) {
+      const conflicter = new Conflicter(new TestAdapter(), false, {
+        dryRun: true,
+        ignoreWhitespace: true
+      });
+      conflicter.collision(
+        {
+          path: path.join(__dirname, 'fixtures/file-conflict.txt'),
+          contents: `initial
+                 content
+      `
+        },
+        status => {
+          assert.equal(status, 'skip');
+          done();
+        }
+      );
+    });
+
     it('does not give a conflict with ignoreWhitespace', function(done) {
       const conflicter = new Conflicter(new TestAdapter(), false, {
         ignoreWhitespace: true