GitDSL: Diffs for added and removed files

[bdotdub]

Calling diffForFile unexpectedly returned null for me for a file that was added. It looks like expected behavior per these lines:

danger-js/source/platforms/github/GitHubGit.ts

Line 50 in 72b7c6c

const modifiedDiffs = fileDiffs.filter((diff: any) => !includes(addedDiffs, diff) && !includes(removedDiffs, diff))

danger-js/source/platforms/github/GitHubGit.ts

Line 150 in 72b7c6c

const structuredDiff = modifiedDiffs.find((diff: any) => diff.from === filename || diff.to === filename)

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It was initially unclear to me why diffForFile would strictly return the diffs for modified files only. I can understand why we would want this conceptually (diffs are a byproduct of a change of a file), but there is definitely utility in being able to get a diff for created and removed files.

I'd like to propose that diffForFile return a TextDiff object for added & removed files. For added files, added will be the whole file and removed would be empty, and vice versa for removed files.

It would make getting all changes in the whole PR much easier, rather than calling diff on some, and fileContents on others:

danger.git.created_files
      .concat(danger.git.modified_files)
      .concat(danger.git.deleted_files)
      .map(p => danger.git.diffForFile(p))

// vs.

danger.git.modified_files
      .map(p => danger.git.diffForFile(p))

const pr = danger.github.pr;
danger.git.created_files
      .map(p => danger.github.utils.fileContents(p, pr.head.repo.full_name, pr.head.sha));
danger.git.deleted_files
      .map(p => danger.github.utils.fileContents(p, pr.base.repo.full_name, pr.base.sha));

(The above code also isn't working for me because of #367)

This change would extend to JSONDiffForFile and JSONPatchForFile.

---

Barring that, the documentation should be more explicit in communicating this.

Happy to do the work but wanted to get some thoughts!

[orta]

Yeah, I think this behaviour is a great call 👍 - I think your expectations there are what I'd imagine too

[orta]

This is in 👍