refactor: remove dependency on path-is-inside

package.json

@@ -37,7 +37,6 @@
     "listr": "^0.14.3",
     "log-symbols": "^3.0.0",
     "micromatch": "^4.0.2",
-    "path-is-inside": "^1.0.2",
     "please-upgrade-node": "^3.1.1",
     "string-argv": "^0.3.0",
     "stringify-object": "^3.3.0"

src/generateTasks.js

@@ -1,11 +1,23 @@
 'use strict'
 
 const micromatch = require('micromatch')
-const pathIsInside = require('path-is-inside')
 const path = require('path')
 
 const debug = require('debug')('lint-staged:gen-tasks')
 
+/**
+ * Test if `child` path is inside `parent` path
+ * https://stackoverflow.com/a/45242825
+ *
+ * @param {String} parent
+ * @param {String} child
+ * @returns {Boolean}
+ */
+const isPathInside = (parent, child) => {
+  const relative = path.relative(parent, child)
+  return relative && !relative.startsWith('..') && !path.isAbsolute(relative)
+}
+
 module.exports = async function generateTasks(linters, gitDir, stagedRelFiles) {
   debug('Generating linter tasks')
 
@@ -20,7 +32,7 @@ module.exports = async function generateTasks(linters, gitDir, stagedRelFiles) {
       stagedFiles
         // Only worry about children of the CWD unless the pattern explicitly
         // specifies that it concerns a parent directory.
-        .filter(file => isParentDirPattern || pathIsInside(file, cwd))
+        .filter(file => isParentDirPattern || isPathInside(cwd, file))
         // Make the paths relative to CWD for filtering
         .map(file => path.relative(cwd, file)),
       pattern,