Add support for external templates

Fixes cookpete#49
Closes cookpete#50

README.md

@@ -171,6 +171,12 @@ Then just use `--template` to point to your template:
 auto-changelog --template changelog-template.hbs
 ```
 
+You can also point to an external template by passing in a URL:
+
+```bash
+auto-changelog --template https://example.com/templates/compact.hbs
+```
+
 To see exactly what data is passed in to the templates, you can generate a JSON version of the changelog:
 
 ```bash

package.json

@@ -45,6 +45,7 @@
     "commander": "^2.9.0",
     "handlebars": "^4.0.11",
     "lodash.uniqby": "^4.7.0",
+    "node-fetch": "^2.2.0",
     "parse-github-url": "^1.0.1",
     "semver": "^5.1.0"
   },

src/template.js

@@ -1,8 +1,10 @@
 import { join } from 'path'
 import Handlebars from 'handlebars'
+import fetch from 'node-fetch'
 import { readFile, fileExists } from './utils'
 
 const TEMPLATES_DIR = join(__dirname, '..', 'templates')
+const MATCH_URL = /^https?:\/\/.+/
 
 Handlebars.registerHelper('json', function (object) {
   return new Handlebars.SafeString(JSON.stringify(object, null, 2))
@@ -47,6 +49,10 @@ Handlebars.registerHelper('matches', function (val, pattern, options) {
 })
 
 async function getTemplate (template) {
+  if (MATCH_URL.test(template)) {
+    const response = await fetch(template)
+    return response.text()
+  }
   if (await fileExists(template)) {
     return readFile(template)
   }

test/template.js

@@ -27,6 +27,12 @@ describe('compileTemplate', () => {
     expect(await compileTemplate(path, { releases })).to.equal(expected)
   })
 
+  it('compiles using url path', async () => {
+    const path = 'https://raw.githubusercontent.com/CookPete/auto-changelog/master/templates/compact.hbs'
+    const expected = await readFile(join(__dirname, 'data', 'template-compact.md'))
+    expect(await compileTemplate(path, { releases })).to.equal(expected)
+  })
+
   it('throws an error when no template found', done => {
     compileTemplate('not-found', { releases })
       .then(() => done('Should throw an error'))

yarn.lock

@@ -2847,6 +2847,10 @@ node-fetch@^1.0.1:
     encoding "^0.1.11"
     is-stream "^1.0.1"
 
+node-fetch@^2.2.0:
+  version "2.2.0"
+  resolved "https://registry.yarnpkg.com/node-fetch/-/node-fetch-2.2.0.tgz#4ee79bde909262f9775f731e3656d0db55ced5b5"
+
 node-pre-gyp@^0.6.36:
   version "0.6.38"
   resolved "https://registry.yarnpkg.com/node-pre-gyp/-/node-pre-gyp-0.6.38.tgz#e92a20f83416415bb4086f6d1fb78b3da73d113d"