CPDBear: Fix for crash when many files are given

Until now, the files to run on were given to CPD with
the --files option, which would raise
'OSError: [Errno 7] Argument list too long'. Now, the
files are saved in a temporary file, and that file is
given to CPD with the --filelist option, which takes a
csv file containing a list of files to run on.

Fixes coala/coala#3701

bears/general/CPDBear.py

@@ -1,3 +1,4 @@
+import os
 from shutil import which
 from xml.etree import ElementTree
 
@@ -36,6 +37,7 @@ class CPDBear(GlobalBear):
     AUTHORS_EMAILS = {'[email protected]'}
     LICENSE = 'AGPL-3.0'
     CAN_DETECT = {'Duplication'}
+    TEMP_FILELIST = '.tmp_filelist'
 
     @classmethod
     def check_prerequisites(cls):  # pragma: no cover
@@ -89,11 +91,15 @@ def run(self, language: str, minimum_tokens: int=20,
             '--skip-duplicate-files': skip_duplicate_files}
 
         files = ','.join(self.file_dict.keys())
+        f = open(self.TEMP_FILELIST, 'w')
+        f.write(str(files))
+        f.close()
+
         executable = which('pmd') or which('run.sh')
         arguments = ('bash', executable, 'cpd', '--skip-lexical-errors',
                      '--minimum-tokens', str(minimum_tokens),
                      '--language', self.lowered_lang_dict[language],
-                     '--files', files,
+                     '--filelist', self.TEMP_FILELIST,
                      '--format', 'xml')
 
         arguments += tuple(option
@@ -102,6 +108,11 @@ def run(self, language: str, minimum_tokens: int=20,
 
         stdout_output, _ = run_shell_command(arguments)
 
+        try:
+            os.remove(self.TEMP_FILELIST)
+        except OSError:
+            pass
+
         if stdout_output:
             root = ElementTree.fromstring(stdout_output)