[FEATURE] Add "ignore whitespace" option in diff

[dusatvoj]

• Gitea version (or commit ref):
• Git version: 1.13.0
• Operating system: any
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (provide example URL)
  • No
• Log gist:

Description

Ignore whitespace option in diff like in bitbucket, etc.

Screenshots

[techknowlogick]

This already exists in Gitea.

you can see it in action in this diff: https://gitea.com/gitea/theme/pulls/92/files

[dusatvoj]

@techknowlogick Is it in stable version or dev? I can't see this feature in our self-hosted gitea 1.13.0
I've tried smth like "Click on commit in repo" ... there's no action to ignore whitespace (even on gitea.com instace https://gitea.com/gitea/theme/commit/4d5fbe24b80542109690c95ab53461c4ec6cba9e)
Now I'm looking to our self-hosted gitea to commit view and there's no action even with whitespace only diff lines