Add "resolve" option to createFilter (#61)

* Add option to create a filter relative to a base dir

* Also allow disabling resolution altogether

* Use npm ci for testing, add Node 12 test

* Update dependencies

* Specify the absolute dir in a more platform independent way

* Also resolve strings starting with `\0`

* Remove ability to resolve strings starting with `\0` again

* Update dependencies

.travis.yml

@@ -4,9 +4,10 @@ node_js:
   - "6"
   - "8"
   - "10"
+  - "12"
 env:
   global:
     - BUILD_TIMEOUT=10000
-install: npm install --ignore-scripts
+install: npm ci --ignore-scripts
 before_install:
   - if [[ $TRAVIS_NODE_VERSION -lt 8 ]]; then npm install --global npm@5; fi

README.md

@@ -89,6 +89,18 @@ export default function myPlugin ( options = {} ) {
 }
 ```
 
+If you want to resolve the patterns against a directory other than
+`process.cwd()`, you can additionally pass a `resolve` option:
+
+```js
+var filter = createFilter( options.include, options.exclude, {resolve: '/my/base/dir'} )
+```
+
+If `resolve` is a string, then this value will be used as the base directory.
+Relative paths will be resolved against `process.cwd()` first. If `resolve` is
+`false`, then the patterns will not be resolved against any directory. This can
+be useful if you want to create a filter for virtual module names.
+
 
 ### makeLegalIdentifier