Allow definition/setup via local template instead of cli

[fregante]

Currently the only customization possible is via the global env property, but unfortunately this isn't available everywhere in the workflow and can't be used to customize a workflow template.

I foresee a few ways to reuse existing templates:

Plain merging of a local template (e.g. .github/workflows-ghat/ci.yml) with the remote template

# Fetch template
apply: fregante/ghat/templates/node

# Overwrite existing `on` property with
on:
  - push

Importing single jobs

on:
  - push
jobs:
  test:
    name: Let's test stuff
    apply: fregante/ghat/templates/node#jobs.test # It would only merge the specific jobs.test section
  build:
    needs: test
    steps:
      - run: echo My other steps

An advanced way to customize the templates

For example it could apply some ENVs at merge time like GitHub does with the $default-branch variable:

• because env doesn't support arrays for example, and can't be used in strategy.matrix
• some conditions could be pre-evaluated, so that whole steps/jobs could be dropped/added at merge time instead of just being silenced at run time.

---

Initially defined in https://github.com/sindresorhus/project-ideas/issues/128

[fregante]

The user would:

1. Create the files in .github/workflows-ghat
2. Run $ ghat without any input

This is essentially the same as https://github.com/fregante/ghat/issues/9, except that https://github.com/fregante/ghat/issues/9 refers to just loading the .github/workflows files.

[fregante]

Alternative idea: The "local template" could just be a .js module that can do anything:

// In ghat
require('./.github/workflows/ghat.js'); // if it exists

// In local .github/workflows/ghat.js
const ghat = require('ghat');
(async () => {
	const myWorkflow = await ghat.get('fregante/ghatemplates/file.yml');
	myWorkflow.name = 'Coolio';
	await ghat.save('ci.yml', myWorkflow);
})();

Pros

• No limits

Cons

• Verbose/complex
• Who really needs this? 🤔