Restore ability to accept relative paths

Blocking the acceptance of relative paths by throwing errors
is a relatively harsh change that has made it difficult for
downstream libraries (e.g., eslint) to upgrade.

Given that relative paths have undefined treatment in ".gitignore"
and the usage of this library beyond ".gitignore" behavior, it seems
fair to give downstream users the chance to customize the handling
of these cases for their own cases.

xref: kaelzhang#20

index.d.ts

@@ -49,6 +49,7 @@ export interface Ignore {
 
 interface Options {
  ignorecase?: boolean
+ ignorerelative?: boolean
 }
 
 /**

index.js

@@ -362,7 +362,7 @@ const throwError = (message, Ctor) => {
  throw new Ctor(message)
 }
 
-const checkPath = (path, originalPath, doThrow) => {
+const checkPath = (path, originalPath, doThrow, ignoreRelative = false) => {
  if (!isString(path)) {
  return doThrow(
  `path must be a string, but got \`${originalPath}\``,
@@ -376,7 +376,7 @@ const checkPath = (path, originalPath, doThrow) => {
  }
 
  // Check if it is a relative path
- if (checkPath.isNotRelative(path)) {
+ if (checkPath.isNotRelative(path) && !ignoreRelative) {
  const r = '`path.relative()`d'
  return doThrow(
  `path should be a ${r} string, but got "${originalPath}"`,
@@ -394,12 +394,14 @@ checkPath.convert = p => p
 
 class Ignore {
  constructor ({
- ignorecase = true
+ ignorecase = true,
+ ignorerelative = false,
  } = {}) {
  define(this, KEY_IGNORE, true)
 
  this._rules = []
  this._ignorecase = ignorecase
+ this._ignorerelative = ignorerelative
  this._initCache()
  }
 
@@ -496,7 +498,7 @@ class Ignore {
  // Supports nullable path
  && checkPath.convert(originalPath)
 
- checkPath(path, originalPath, throwError)
+ checkPath(path, originalPath, throwError, this._ignorerelative)
 
  return this._t(path, cache, checkUnignored, slices)
  }
@@ -559,7 +561,7 @@ const returnFalse = () => false
 const isPathValid = path =>
  checkPath(path && checkPath.convert(path), path, returnFalse)
 
-factory.isPathValid = isPathValid
+factory.isPathValid = path => isPathValid(path)
 
 // Fixes typescript
 factory.default = factory