API Features for automated build tools

[Zuph]

• Gitea version (or commit ref): 1.12.0
• Git version: N/A
• Operating system: N/A
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (provide example URL)
  • No
  • Not relevant
• Log gist:

Description

I'm trying to adapt some Drone plugins to work with Gitea, and I'm running into some missing parts of the API. Specifically

• List Pull Request Files (/repos/:owner/:repo/pulls/:pull_number/files, https://developer.github.com/v3/pulls/#list-pull-requests-files) (Possibly addressed by api/v1/repos/:owner/:repo/pulls/*** not implemented #3472 ?)
• Compare two commits (/repos/:owner/:repo/compare/:base...:head, https://developer.github.com/v3/repos/commits/#compare-two-commits)

I'm happy to hack around and try and add these, but I wanted to document the want in case my Go skills aren't quite up to it 😃

[6543]

as for documenting ... -> https://github.com/go-gitea/gitea/blob/master/CONTRIBUTING.md#api-v1 ;)

@Zuph sure go on creating a pull if you like