recreate: remove special-cased --dry-run

src/borg/archive.py

@@ -1394,10 +1394,6 @@ def finish(self, save_space=False):
 
 
 class ArchiveRecreater:
-    class FakeTargetArchive:
-        def __init__(self):
-            self.stats = Statistics()
-
     class Interrupted(Exception):
         def __init__(self, metadata=None):
             self.metadata = metadata or {}
@@ -1434,7 +1430,7 @@ def __init__(self, repository, manifest, key, cache, matcher,
         self.stats = stats
         self.progress = progress
         self.print_file_status = file_status_printer or (lambda *args: None)
-        self.checkpoint_interval = checkpoint_interval
+        self.checkpoint_interval = None if dry_run else checkpoint_interval
 
     def recreate(self, archive_name, comment=None, target_name=None):
         assert not self.is_temporary_archive(archive_name)
@@ -1444,7 +1440,7 @@ def recreate(self, archive_name, comment=None, target_name=None):
             self.matcher_add_tagged_dirs(archive)
         if self.matcher.empty() and not self.recompress and not target.recreate_rechunkify and comment is None:
             logger.info("Skipping archive %s, nothing to do", archive_name)
-            return True
+            return
         self.process_items(archive, target)
         replace_original = target_name is None
         self.save(archive, target, comment, replace_original=replace_original)
@@ -1588,8 +1584,6 @@ def exclude(dir, tag_item):
 
     def create_target(self, archive, target_name=None):
         """Create target archive."""
-        if self.dry_run:
-            return self.FakeTargetArchive(), None
         target_name = target_name or archive.name + '.recreate'
         target = self.create_target_archive(target_name)
         # If the archives use the same chunker params, then don't rechunkify

src/borg/archiver.py

@@ -1102,9 +1102,10 @@ def do_recreate(self, args, repository, manifest, key, cache):
                     continue
                 print('Processing', name)
                 recreater.recreate(name, args.comment)
-        manifest.write()
-        repository.commit()
-        cache.commit()
+        if not args.dry_run:
+            manifest.write()
+            repository.commit()
+            cache.commit()
         return self.exit_code
 
     @with_repository(manifest=False, exclusive=True)
@@ -2387,8 +2388,8 @@ def build_parser(self, prog=None):
 
         When rechunking space usage can be substantial, expect at least the entire
         deduplicated size of the archives using the previous chunker params.
-        When recompressing approximately 1 % of the repository size or 512 MB
-        (whichever is greater) of additional space is used.
+        When recompressing expect approx throughput / checkpoint-interval in space usage,
+        assuming all chunks are recompressed.
         """)
         subparser = subparsers.add_parser('recreate', parents=[common_parser], add_help=False,
                                           description=self.do_recreate.__doc__,