Diff parsing fails with opaque error when SSH warnings preceed the standard header

[aalong-tr]

Subject of the issue

I'm experiencing a transient error in a CI environment using the Danger gem. The exception and relevant stack trace:

undefined method `[]' for nil:NilClass
/home/circleci/repo/vendor/bundle/ruby/2.7.0/gems/git-1.10.2/lib/git/diff.rb:148:in `block in process_full_diff'
/home/circleci/repo/vendor/bundle/ruby/2.7.0/gems/git-1.10.2/lib/git/diff.rb:131:in `each'
/home/circleci/repo/vendor/bundle/ruby/2.7.0/gems/git-1.10.2/lib/git/diff.rb:131:in `process_full_diff'
/home/circleci/repo/vendor/bundle/ruby/2.7.0/gems/git-1.10.2/lib/git/diff.rb:110:in `process_full'
/home/circleci/repo/vendor/bundle/ruby/2.7.0/gems/git-1.10.2/lib/git/diff.rb:68:in `each

I have identified the root cause as git diff output that includes an SSH key warning:

Warning: Permanently added the ECDSA host key for IP address '000.00.000.0' to the list of known hosts.
diff --git a/some/file/name b/some/file/name

(IP address obscured)

While SSH warnings are not necessarily the responsibility of this gem, better error handling with explicit explanation of why the git diff output did not match expected formatting would make this style of error significantly easier to identify and fix.

Your environment

• ruby-git version 1.10.2
• Ruby version 2.7.0

[aalong-tr]

Proposed fix in #585

[jcouball]

Fixed with #684 and released in git-2.0.0-pre1

[aalong-tr]

Fabulous news, thank you so much for this refactor!