add --dry-run feature check

borgmatic/borg/compact.py

@@ -1,7 +1,7 @@
 import logging
 
 import borgmatic.config.paths
-from borgmatic.borg import environment, flags
+from borgmatic.borg import environment, feature, flags
 from borgmatic.execute import execute_command
 
 logger = logging.getLogger(__name__)
@@ -42,7 +42,12 @@ def compact_segments(
     )
 
     if dry_run:
-        logging.info('Skipping compact (dry run)')
+        if feature.available(feature.Feature.DRY_RUN_COMPACT, local_borg_version):
+            logging.info('Skipping compact (dry run)')
+        else:
+            logging.warning(
+                'The --dry-run option is not supported for compact in the current version of Borg.'
+            )
         return
 
     execute_command(

borgmatic/borg/feature.py

@@ -18,6 +18,7 @@ class Feature(Enum):
     EXCLUDED_FILES_MINUS = 12
     ARCHIVE_SERIES = 13
     NO_PRUNE_STATS = 14
+    DRY_RUN_COMPACT = 15
 
 
 FEATURE_TO_MINIMUM_BORG_VERSION = {
@@ -35,6 +36,7 @@ FEATURE_TO_MINIMUM_BORG_VERSION = {
     Feature.EXCLUDED_FILES_MINUS: parse('2.0.0b5'),  # --list --filter uses "-" for excludes
     Feature.ARCHIVE_SERIES: parse('2.0.0b11'),  # identically named archives form a series
     Feature.NO_PRUNE_STATS: parse('2.0.0b10'),  # prune --stats is not available
+    Feature.DRY_RUN_COMPACT: parse('1.4.1'),  # borg compact --dry-run support
 }
 
 

tests/unit/borg/test_compact.py

@@ -69,8 +69,25 @@ def test_compact_segments_with_log_debug_calls_borg_with_debug_flag():
 
 
 def test_compact_segments_with_dry_run_skips_borg_call():
+    # Test borg version supports dry run.
+    logger_mock = flexmock(logging)
+    logger_mock.should_receive('info').with_args('Skipping compact (dry run)').once()
+
     flexmock(module).should_receive('execute_command').never()
 
+    module.compact_segments(
+        repository_path='repo',
+        config={},
+        local_borg_version='1.4.1',
+        global_arguments=flexmock(),
+        dry_run=True,
+    )
+
+    # Test borg version that does not support dry run.
+    logger_mock.should_receive('warning').with_args(
+        'The --dry-run option is not supported for compact in the current version of Borg.'
+    ).once()
+
     module.compact_segments(
         repository_path='repo',
         config={},