run-when 

> Run tasks based on git diff files

$3

Having this directory tree with the following files changed:

``
├── app
├────── components
├ ├── index.js
├ ├── app.jsx
└── __tests__
├ ├── app.spec.jsx
└── package.json
`

`run-when` will check glob rules against it and run tasks if any changes have been made.

#### Javascript

`javascript
import runWhen from 'run-when';

runWhen([
{
glob: ['app/components/index.js', 'app/__tests__/**'],
task(paths) {
console.log('This will be called!');
}
},
{
glob: ['!package.json'],
task(paths) {
return Promise.resolve('You can return a promise from your task');
}
},
{
// Optionally pass changed files
changedFiles: () => Promise.resolve(['app/index.js', 'app/components/header.jsx']),
glob: ['app/components/**'],
task(paths) {
console.log(paths === ['app/components/header.jsx']);
}
}
]);

`

#### CLI

`
$ run-when '["app/components/", "app/utils/"]' 'echo running tests... && yarn test'
`

* First argument is a stringified JSON containing glob patterns.
* Second argument is the task to run.

#### How it works

By default `run-when` will use git to know which files have been changed. You can change that
passing an array of files to `changedFiles`.

#### Globbing pattern

The library uses multimatch for the globbing matching (sindresorhus 😻). Just a quick overview:

- * matches any number of characters, but not /
- ? matches a single character, but not /
- ** matches any number of characters, including /, as long as it's the only thing in a path part
- {} allows for a comma-separated list of "or" expressions
- ! at the beginning of a pattern will negate the match

Various patterns and expected matches.

#### Api

`typescript
type Files = Array;
`

`typescript
interface Rule {
glob: Array,
task: (results: Files) => void,
changedFiles?: () => Promise
}
`

`typescript
type runWhen = (rules: Array) => Promise;
`

#### Installation

`
$ yarn add run-when -D
``