Options that expect a file should accept lists of files too

The rationale is that these options readily accept multiple files from
the command line, because they can be specified multiple times. However,
duplicate option keys are invalid in an INI config file. The alternative
is to accept multiple values for each occurrence of an option key.

codespell_lib/_codespell.py

@@ -339,10 +339,9 @@ def parse_options(
         "-D",
         "--dictionary",
         action="append",
-        help="custom dictionary file that contains spelling "
-        "corrections. If this flag is not specified or "
-        'equals "-" then the default dictionary is used. '
-        "This option can be specified multiple times.",
+        help="comma-separated list of custom dictionary files that "
+        "contain spelling  corrections. If this flag is not specified "
+        'or equals "-" then the default dictionary is used.',
     )
     builtin_opts = "\n- ".join(
         [""] + [f"{d[0]!r} {d[1]}" for d in _builtin_dictionaries]
@@ -372,26 +371,26 @@ def parse_options(
         "-I",
         "--ignore-words",
         action="append",
-        metavar="FILE",
-        help="file that contains words that will be ignored "
-        "by codespell. File must contain 1 word per line."
-        " Words are case sensitive based on how they are "
-        "written in the dictionary file",
+        metavar="FILES",
+        help="comma-separated list of files that contain "
+        "words to be ignored by codespell. Files must contain "
+        "1 word per line. Words are case sensitive based on "
+        "how they are  written in the dictionary file.",
     )
     parser.add_argument(
         "-L",
         "--ignore-words-list",
         action="append",
         metavar="WORDS",
-        help="comma separated list of words to be ignored "
+        help="comma-separated list of words to be ignored "
         "by codespell. Words are case sensitive based on "
-        "how they are written in the dictionary file",
+        "how they are written in the dictionary file.",
     )
     parser.add_argument(
         "--uri-ignore-words-list",
         action="append",
         metavar="WORDS",
-        help="comma separated list of words to be ignored "
+        help="comma-separated list of words to be ignored "
         "by codespell in URIs and emails only. Words are "
         "case sensitive based on how they are written in "
         'the dictionary file. If set to "*", all '
@@ -443,11 +442,13 @@ def parse_options(
     parser.add_argument(
         "-x",
         "--exclude-file",
+        action="append",
         type=str,
-        metavar="FILE",
-        help="ignore whole lines that match those "
-        "in the file FILE. The lines in FILE "
-        "should match the to-be-excluded lines exactly",
+        metavar="FILES",
+        help="ignore whole lines that match those in "
+        "the comma-separated list of files EXCLUDE. "
+        "The lines in these files should match the "
+        "to-be-excluded lines exactly",
     )
 
     parser.add_argument(
@@ -1028,7 +1029,10 @@ def main(*args: str) -> int:
     else:
         ignore_word_regex = None
 
-    ignore_words_files = options.ignore_words or []
+    ignore_words_files = []
+    if options.ignore_words:
+        for iw in options.ignore_words:
+            ignore_words_files.extend(iw.split(","))
     ignore_words = parse_ignore_words_option(options.ignore_words_list)
     for ignore_words_file in ignore_words_files:
         if not os.path.isfile(ignore_words_file):
@@ -1053,7 +1057,9 @@ def main(*args: str) -> int:
     uri_ignore_words = parse_ignore_words_option(options.uri_ignore_words_list)
 
     if options.dictionary:
-        dictionaries = options.dictionary
+        dictionaries = []
+        for d in options.dictionary:
+            dictionaries.extend(d.split(","))
     else:
         dictionaries = ["-"]
     use_dictionaries = []
@@ -1119,7 +1125,9 @@ def main(*args: str) -> int:
 
     exclude_lines: Set[str] = set()
     if options.exclude_file:
-        build_exclude_hashes(options.exclude_file, exclude_lines)
+        for exclude_file_list in options.exclude_file:
+            for exclude_file in exclude_file_list.split(","):
+                build_exclude_hashes(exclude_file, exclude_lines)
 
     file_opener = FileOpener(options.hard_encoding_detection, options.quiet_level)