feat: add --staged flag

README.md

@@ -61,16 +61,25 @@ yarn add --dev husky
 In `package.json`'s `"scripts"` section, add:
 
 ```
-"precommit": "pretty-quick --since HEAD"
+"precommit": "pretty-quick --staged"
 ```
 
+## CLI Flags
 
+### `--staged`
 
-## CLI Flags
+Pre-commit mode. Under this flag only staged files will be formatted, and they will be re-staged after formatting.
+
+<!-- Undocumented = Unsupported :D
+
+### `--add`
+
+Restage files that are formatted.
 
 ### `--since`
 
 A SCM revision such as a git commit hash or ref.
 
 For example `pretty-quick --since HEAD` will format only staged files.
 
+-->

bin/pretty-quick.js

@@ -16,16 +16,18 @@ prettyQuick(
       console.log(
         `🔍  Finding changed files since ${chalk.bold(
           scm
-        )} revision ${chalk.bold(revision)}`
+        )} revision ${chalk.bold(revision)}.`
       );
     },
+
     onFoundChangedFiles: changedFiles => {
       console.log(
         `🎯  Found ${changedFiles.length} ${
           changedFiles.length === 1 ? 'file' : 'files'
         } changed.`
       );
     },
+
     onWriteFile: file => {
       console.log(`✍️  Fixing up ${chalk.bold(file)}.`);
     },

package.json

@@ -24,7 +24,7 @@
     "test": "jest",
     "lint": "eslint . --ignore-path=.gitignore",
     "semantic-release": "semantic-release",
-    "precommit": "pretty-quick --since HEAD"
+    "precommit": "./bin/pretty-quick.js --staged"
   },
   "peerDependencies": {
     "prettier": ">=1.8.0"

src/formatFiles.js

@@ -13,8 +13,8 @@ export default (files, { config, onWriteFile }) => {
     );
 
     if (output !== input) {
-      onWriteFile && onWriteFile(file);
       writeFileSync(file, output);
+      onWriteFile && onWriteFile(file);
     }
   }
 };

src/index.js

@@ -7,14 +7,21 @@ import isSupportedExtension from './isSupportedExtension';
 
 export default (
   directory,
-  { since, config, onFoundSinceRevision, onFoundChangedFiles, onWriteFile }
+  {
+    config,
+    since,
+    staged,
+    onFoundSinceRevision,
+    onFoundChangedFiles,
+    onWriteFile,
+  }
 ) => {
   const scm = scms(directory);
   if (!scm) {
     throw new Error('Unable to detect a source control manager.');
   }
 
-  const revision = since || scm.getSinceRevision(directory);
+  const revision = since || scm.getSinceRevision(directory, { staged });
 
   onFoundSinceRevision && onFoundSinceRevision(scm.name, revision);
 
@@ -26,5 +33,11 @@ export default (
 
   onFoundChangedFiles && onFoundChangedFiles(changedFiles);
 
-  formatFiles(changedFiles, { config, onWriteFile });
+  formatFiles(changedFiles, {
+    config,
+    onWriteFile: file => {
+      onWriteFile(file);
+      scm.stageFile(directory, file);
+    },
+  });
 };

src/scms/git.js

@@ -19,7 +19,10 @@ const runGit = (directory, args) =>
 
 const getLines = execaResult => execaResult.stdout.split('\n');
 
-export const getSinceRevision = directory => {
+export const getSinceRevision = (directory, { staged }) => {
+  if (staged) {
+    return 'HEAD';
+  }
   return runGit(directory, ['merge-base', 'HEAD', 'master']).stdout.trim();
 };
 
@@ -38,3 +41,7 @@ export const getChangedFiles = (directory, revision) => {
     ),
   ].filter(Boolean);
 };
+
+export const stageFile = (directory, file) => {
+  runGit(directory, ['add', file]);
+};