[Feature:Plagiarism] Subtractive regex for student files (#56)

* Add ability to exclude files by putting an "!" before regex

* "!" character removes files from the selection instead of adding everything except files

Author: williamjallen

bin/concatenate_all.py

@@ -29,8 +29,18 @@ def getConcatFilesInDir(input_dir, regex_patterns):
         files = sorted(my_files)
         if regex_patterns[0] != "":
             files_filtered = []
+            # resolve all of the additions
             for e in regex_patterns:
-                files_filtered.extend(fnmatch.filter(files, e.strip()))
+                # Regex patterns starting with a ! indicate that files should be excluded
+                if not e.strip().startswith("!"):
+                    files_filtered.extend(fnmatch.filter(files, e.strip()))
+
+            # resolve the subtractions
+            for e in regex_patterns:
+                if e.strip().startswith("!"):
+                    files_filtered = [file for file in files_filtered if file not in
+                                      fnmatch.filter(files_filtered, e.strip().replace("!", ""))]
+
             files = files_filtered
 
         for my_file in files: