Feature: provider-agnostic API to fetch file contents of a different ref

Describe the bug danger.github is undefined.

Cannot read property 'pr' of undefined
TypeError: Cannot read property 'pr' of undefined
    at dangerfile.js:5:62

To Reproduce

• git clone https://github.com/edno/danger-github-undefined.git
• cd danger-github-undefined
• yarn install (Yarn 2)
• git checkout new-branch
• yarn danger local -b main

Expected behavior This should display

message(`:tada: The PR added ${additions} and removed ${deletions} lines.`)

Environment

software	version
danger.js	^10.6.2
node	v12.18.3
yarn	2.4.0
Operating System	MacOS 11.2.1

[orta]

Yep, good thinking, I’d accept a PR adding an API something like:

import {danger} from "danger"

 // could maybe be always "HEAD", but could also be a branch reference, hard to say what it should be with --staging though
danger.local.head
 
// master, or whatever someone changed it to
danger.local.base 

// New to .git - when in `local` use wrapped git call, otherwise use the available APIs 
// Defaults to the head version
danger.git.getFileContents("file.md")

// So, you can get the other SHA refs
danger.git.getFileContents("file.md", danger.local.base)

[orta]

I don’t think there’s an API for that today, I have generally only looked at the files which changed and not necessarily the contents - I think there could be a danger.local API which feels like github which wraps calls to git to provide those sorts of functions?