Allow folding indented code blocks below ‘when’ statements

Since when statements can have their code “inline”, e.g. “when match: do_something” we match lines with ‘when’ keywords either not containing any ‘then’ or colon (‘:’), or where ‘then’ or colon are the last things on the line (except for a trailing line comment).

Author: sorbits

Preferences/Folding.tmPreferences

@@ -8,6 +8,13 @@
 	<string>source.ruby -string.unquoted.heredoc</string>
 	<key>settings</key>
 	<dict>
+		<key>foldingIndentedBlockStart</key>
+		<string>(?x)
+        ^ \s+ when \s
+        (     .*  (\s then | :) \s* (\#.*)? $
+        | (?! .*? (\s then | :) \s+ [^#\s] )
+        )
+    </string>
 		<key>foldingStartMarker</key>
 		<string>(?x)^
 	    (\s*+