Added --keep-all, as an alias for '--keep-last <inf>', as an option for borg-prune. Fixes #6656

Author: Michael Deyaso

src/borg/archiver/prune_cmd.py

@@ -138,7 +138,7 @@ def do_prune(self, args, repository, manifest):
                 'At least one of the "keep-within", "keep-last", '
                 '"keep-secondly", "keep-minutely", "keep-hourly", "keep-daily", '
                 '"keep-weekly", "keep-monthly", "keep-13weekly", "keep-3monthly", '
-                'or "keep-yearly" settings must be specified.'
+                '"keep-yearly", or "keep-all" settings must be specified.'
             )
 
         if args.format is not None:
@@ -320,6 +320,13 @@ def build_parser_prune(self, subparsers, common_parser, mid_common_parser):
             action=Highlander,
             help="number of secondly archives to keep",
         )
+        subparser.add_argument(
+            "--keep-all",
+            dest="secondly",
+            action="store_const",
+            const=float("inf"),
+            help="keep all archives (alias of --keep-last=<infinite>)",
+        )
         subparser.add_argument(
             "--keep-minutely",
             dest="minutely",