update Dangerfile

Dangerfile

@@ -1,20 +1,42 @@
-
-# Make it more obvious that a PR is a work in progress and shouldn't be merged yet
-warn("PR is classed as Work in Progress", sticky: true) if github.pr_title.include? "[WIP]"
+# PR is a work in progress and shouldn't be merged yet
+warn "PR is classed as Work in Progress" if github.pr_title.include? "[WIP]"
 
 # Warn when there is a big PR
-warn("Big PR", sticky: true) if git.lines_of_code > 500
+warn "Big PR, consider splitting into smaller" if git.lines_of_code > 500
+
+# Ensure a clean commits history
+if git.commits.any? { |c| c.message =~ /^Merge branch '#{github.branch_for_base}'/ }
+  fail "Please rebase to get rid of the merge commits in this PR"
+end
+
+# Mainly to encourage writing up some reasoning about the PR, rather than
+# just leaving a title
+if github.pr_body.length < 5
+  fail "Please provide a summary in the Pull Request description"
+end
+
+# If these are all empty something has gone wrong, better to raise it in a comment
+if git.modified_files.empty? && git.added_files.empty? && git.deleted_files.empty?
+  fail "This PR has no changes at all, this is likely an issue during development."
+end
 
-## Let's check if there are any changes in the project folder
 has_app_changes = !git.modified_files.grep(/ProjectName/).empty?
-## Then, we should check if tests are updated
 has_test_changes = !git.modified_files.grep(/ProjectNameTests/).empty?
-## Finally, let's combine them and put extra condition 
-## for changed number of lines of code
-if has_app_changes && !has_test_changes && git.lines_of_code > 20
+
+# If changes are more than 10 lines of code, tests need to be updated too
+if has_app_changes && !has_test_changes && git.lines_of_code > 10
   fail("Tests were not updated", sticky: false)
 end
 
-# SwiftLint
-swiftlint.config_file = '.swiftlint.yml'
-swiftlint.lint_files inline_mode: true
+# Info.plist file shouldn't change often. Leave warning if it changes.
+is_plist_change = git.modified_files.sort == ["ProjectName/Info.plist"].sort
+
+if !is_plist_change
+  warn "Plist changed, don't forget to localize your plist values"
+end
+
+# This is swiftlint plugin. More info: https://github.com/ashfurrow/danger-swiftlint
+#
+# This lints all Swift files and leave comments in PR if 
+# there is any issue with linting
+swiftlint.lint_files inline_mode: true