feat: do the thing

.babelrc

@@ -0,0 +1,3 @@
+{
+  "presets": [["env", { "targets": { "node": "6.10" } }]]
+}

.eslintrc.yml

@@ -0,0 +1,13 @@
+extends:
+- eslint:recommended
+- plugin:jest/recommended
+- plugin:prettier/recommended
+env:
+  es6: true
+  node: true
+rules:
+  no-console: off
+overrides:
+- files: "src/**/*.js"
+  parserOptions:
+    sourceType: module

.gitignore

@@ -1,2 +1,3 @@
 node_modules
 *.log
+dist

.prettierignore

@@ -0,0 +1 @@
+package.json

.prettierrc.yml

@@ -0,0 +1,2 @@
+trailingComma: es5
+singleQuote: true

README.md

@@ -1,3 +1,39 @@
 # `pretty-quick`
 
 > Get Pretty Quick
+
+Runs [Prettier](https://prettier.io) on your changed files.
+
+Supported source control managers:
+
+* Git
+* _Add more_
+
+## Install
+
+With `yarn`:
+
+```shellsession
+yarn add --dev pretty-quick
+```
+
+With `npm`:
+
+```shellsession
+npm install --save-dev pretty-quick
+```
+
+## Usage
+
+With `yarn`:
+
+```shellsession
+yarn pretty-quick
+```
+
+With `npm`:
+
+1. Add `"pretty-quick": "pretty-quick"` to the scripts section of `package.json`.
+2. ```shellsession
+   npm run pretty-quick
+   ```

bin/pretty-quick.js

@@ -1,9 +1,35 @@
 #!/usr/bin/env node
 
-"use strict";
+'use strict';
 
-const prettier = require('prettier');
+const chalk = require('chalk');
 const mri = require('mri');
 
+const prettyQuick = require('..').default;
+
 const args = mri(process.argv.slice(2));
 
+prettyQuick(
+  process.cwd(),
+  Object.assign({}, args, {
+    onFoundSinceRevision: (scm, revision) => {
+      console.log(
+        `🔍  Finding changed files since ${chalk.bold(
+          scm
+        )} 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)}.`);
+    },
+  })
+);
+
+console.log('✅  Everything is awesome!');

package.json

@@ -4,12 +4,36 @@
   "description": "Get Pretty Quick",
   "repository": "azz/pretty-quick",
   "author": "Lucas Azzola <@azz>",
+  "main": "./dist",
   "bin": "./bin/pretty-quick",
   "license": "MIT",
+  "files": [
+    "bin",
+    "dist"
+  ],
   "dependencies": {
+    "chalk": "^2.3.0",
+    "execa": "^0.8.0",
+    "ignore": "^3.3.7",
     "mri": "^1.1.0"
   },
+  "scripts": {
+    "prepublishOnly": "yarn build",
+    "build": "babel src -d dist --copy-files",
+    "test": "jest"
+  },
   "peerDependencies": {
-    "prettier": "^1.9.2"
+    "prettier": ">=1.8.0"
+  },
+  "devDependencies": {
+    "babel-cli": "^6.26.0",
+    "babel-core": "^6.26.0",
+    "babel-preset-env": "^1.6.1",
+    "eslint": "^4.15.0",
+    "eslint-config-prettier": "^2.9.0",
+    "eslint-plugin-jest": "^21.5.0",
+    "eslint-plugin-prettier": "^2.4.0",
+    "jest": "^22.0.4",
+    "prettier": "1.9.2"
   }
 }

src/createIgnorer.js

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+import { existsSync, readFileSync } from 'fs';
+import { join } from 'path';
+import ignore from 'ignore';
+
+export default (directory, filename = '.prettierignore') => {
+  const file = join(directory, filename);
+  if (existsSync(file)) {
+    const text = readFileSync(file, 'utf8');
+    return ignore()
+      .add(text)
+      .createFilter();
+  }
+
+  return () => true;
+};

src/formatFiles.js

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+import { readFileSync, writeFileSync } from 'fs';
+import { resolveConfig, format } from 'prettier';
+
+export default (files, { config, onWriteFile }) => {
+  for (const file of files) {
+    const options = resolveConfig.sync(file, { config });
+    const input = readFileSync(file, 'utf8');
+    const output = format(
+      input,
+      Object.assign(options, {
+        filepath: file,
+      })
+    );
+
+    if (output !== input) {
+      onWriteFile && onWriteFile(file);
+      writeFileSync(file, output);
+    }
+  }
+};

src/index.js

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+import { relative } from 'path';
+
+import scms from './scms';
+import formatFiles from './formatFiles';
+import createIgnorer from './createIgnorer';
+import isSupportedExtension from './isSupportedExtension';
+
+export default (
+  directory,
+  { since, config, 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);
+
+  onFoundSinceRevision && onFoundSinceRevision(scm.name, revision);
+
+  const changedFiles = scm
+    .getChangedFiles(directory, revision)
+    .map(file => relative(directory, file))
+    .filter(isSupportedExtension)
+    .filter(createIgnorer(directory));
+
+  onFoundChangedFiles && onFoundChangedFiles(changedFiles);
+
+  formatFiles(changedFiles, { config, onWriteFile });
+};

src/isSupportedExtension.js

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+import { extname } from 'path';
+import { getSupportInfo } from 'prettier';
+
+const extensions = getSupportInfo().languages.reduce(
+  (prev, language) => prev.concat(language.extensions || []),
+  []
+);
+
+export default file => extensions.includes(extname(file));

src/scms/git.js

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+import { statSync } from 'fs';
+import { join } from 'path';
+import execa from 'execa';
+
+export const name = 'git';
+
+export const detect = directory => {
+  try {
+    return statSync(join(directory, '.git')).isDirectory();
+  } catch (error) {
+    return false;
+  }
+};
+
+const runGit = (directory, args) =>
+  execa.sync('git', args, {
+    cwd: directory,
+  });
+
+const getLines = execaResult => execaResult.stdout.split('\n');
+
+export const getSinceRevision = directory => {
+  return runGit(directory, ['merge-base', 'HEAD', 'master']).stdout.trim();
+};
+
+export const getChangedFiles = (directory, revision) => {
+  return [
+    ...getLines(
+      runGit(directory, [
+        'diff',
+        '--name-only',
+        '--diff-filter=ACMRTUB',
+        revision,
+      ])
+    ),
+    ...getLines(
+      runGit(directory, ['ls-files', '--others', '--exclude-standard'])
+    ),
+  ].filter(Boolean);
+};

src/scms/index.js

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+import * as gitScm from './git';
+
+const scms = [gitScm];
+
+export default directory => {
+  for (const scm of scms) {
+    if (scm.detect(directory)) {
+      return scm;
+    }
+  }
+};