feat(display): improve the informational output when running the CLI

`codemod` now prints all files it runs with, but dims those where there are no changes. This is similar to what prettier does.

src/index.ts

@@ -63,9 +63,9 @@ EXAMPLES
 
 export default async function run(
   argv: Array<string>,
-  stdin: NodeJS.ReadableStream,
-  stdout: NodeJS.WritableStream,
-  stderr: NodeJS.WritableStream,
+  stdin: NodeJS.ReadStream,
+  stdout: NodeJS.WriteStream,
+  stderr: NodeJS.WriteStream,
   fs: typeof realFs = realFs
 ): Promise<number> {
   let options = Options.parse(argv.slice(2));
@@ -119,12 +119,17 @@ export default async function run(
 
   runner = new TransformRunner(sourcesIterator, plugins);
 
+  let dim = stdout.isTTY ? '\x1b[2m' : '';
+  let reset = stdout.isTTY ? '\x1b[0m' : '';
+
   for (let result of runner.run()) {
     if (result.output) {
       if (options.stdio) {
         stdout.write(`${result.output}\n`);
       } else {
-        if (result.output !== result.source.content) {
+        if (result.output === result.source.content) {
+          stdout.write(`${dim}${result.source.path}${reset}\n`);
+        } else {
           stats.modified++;
           stdout.write(`${result.source.path}\n`);
           if (!dryRun) {

test/cli/CLITest.ts

@@ -141,6 +141,21 @@ describe('CLI', function() {
     strictEqual(await readFile(afile, 'utf8'), '3 + 4;');
   });
 
+  it('prints files not processed in dim colors', async function() {
+    let afile = await createTemporaryFile('a-file.js', '3 + 4;');
+    let { status, stdout, stderr } = await runCodemodCLI([afile]);
+
+    deepEqual(
+      { status, stdout, stderr },
+      {
+        status: 0,
+        stdout: `${afile}\n1 file(s), 0 modified, 0 errors\n`,
+        stderr: ''
+      }
+    );
+    strictEqual(await readFile(afile, 'utf8'), '3 + 4;');
+  });
+
   it('can load plugins written with ES modules by default', async function() {
     let afile = await createTemporaryFile('a-file.js', '3 + 4;');
     let { status, stdout, stderr } = await runCodemodCLI([