Delete a file using signed commits

do_magic.rb

# This code is based upon the following links:
#   https://developer.github.com/v3/git/trees/
#   https://github.com/testcollab/rails-test
#   https://stackoverflow.com/questions/23637961/how-do-i-mark-a-file-as-deleted-in-a-tree-using-the-github-api
#   https://github.community/t/deleting-files-via-trees-no-longer-works/14042

# This creates a signed commit on the correct branch, but there are 0 changed files.


# THIS IS THE METHOD THAT IS CALLED BY THE MAIN PROCESS TO REMOVE FILES
def commit_files_to_remove
  last_commit_sha = last_commit_from_branch # get last commit
  last_tree_sha = tree_sha_for(last_commit_sha) # get base tree

  clean_tree = github.git_data.trees.create @repo.username, @repo.repo_name,
                                            tree: clean_branch_badge_tree_files(new_branch_sha),
                                            base_tree: last_tree_sha
  # RESPONSE WRITTEN TO 'clean_tree.txt'

  body = { message: 'Remove evaluation.json',
           tree: clean_tree.sha,
           parents: [last_commit_sha],
           author: commit_author,
           committer: commit_author,
           signature: signature(tree_sha: clean_tree.sha, parent_sha: last_commit_sha) }

  resp = Faraday.post(commit_url, body.to_json, commit_headers)
  commit = JSON.parse(resp.body)
  # RESPONSE WRITTEN TO 'commit.txt'

  github.git_data.references.update @repo.username, @repo.repo_name,
                                    "heads/#{branch_name}",
                                    sha: commit['sha']
  # RESPONSE WRITTEN TO 'update_reference.txt'
end

def last_commit_from_branch
  resp = Faraday.get("https://api.github.com/repos/#{@repo.username}/#{@repo.repo_name}/git/ref/heads/#{branch_name}",
                     nil,
                     commit_headers)
  # RESPONSE WRITTEN TO 'last_commit_from_branch.txt'
  JSON.parse(resp.body)['object']['sha']
end

def tree_sha_for(commit_sha)
  resp = Faraday.get("https://api.github.com/repos/#{@repo.username}/#{@repo.repo_name}/git/commits/#{commit_sha}",
                     nil,
                     commit_headers)
  # RESPONSE WRITTEN TO 'tree_sha_for.txt'
  JSON.parse(resp.body)['tree']['sha']
end

def clean_branch_badge_tree_files(sha)
  # get the base branch tree that has all of the files in it
  branch_tree = github.git_data.trees.get @repo.username,
                                          @repo.repo_name,
                                          sha,
                                          recursive: true
  # RESPONSE WRITTEN TO 'branch_tree.txt'

  # select only the files in a matching subdirectory
  badge_tree_files = branch_tree.tree.select { |f| f['path'].include?("/#{api_name}/") }

  # exclude any evaluation.json file(s) from the tree to delete
  badge_tree_files.reject { |f| f['path'].end_with?('evaluation.json') }
  # badge_tree_files FILES WRITTEN TO 'clean_branch_badge_tree_files.txt'
end

def new_branch_sha
  @new_branch_sha ||= find_branch_sha(branch_name)
end

def find_branch_sha(branch_name)
  refs = github.git_data.references.list @repo.username, @repo.repo_name
  results = refs.select { |r| r.ref.eql?("refs/heads/#{branch_name}") }
  results.first.object.sha
rescue NoMethodError
  raise "Github branch '#{branch_name}' not found."
end

def commit_url
  "https://api.github.com/repos/#{@repo.username}/#{@repo.repo_name}/git/commits"
end

def commit_headers
  {'Content-Type' => 'application/json', 'Authorization' => "token #{@repo.token}"}
end