From f495550ad7fdfb95e1d25d0a7c134e3490abc5da Mon Sep 17 00:00:00 2001
From: Dan <dan@energysavvy.com>
Date: Sun, 29 Oct 2017 20:14:18 -0700
Subject: [PATCH] Default "prefix" to "{hostname}-" if not specified.

---
 NEWS                                    | 3 ++-
 borgmatic/borg/prune.py                 | 3 +++
 borgmatic/config/schema.yaml            | 2 +-
 borgmatic/tests/unit/borg/test_prune.py | 4 ++--
 4 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/NEWS b/NEWS
index 1b815db1..00c5298d 100644
--- a/NEWS
+++ b/NEWS
@@ -3,7 +3,8 @@
  * #33: Improve clarity of logging spew at high verbosity levels.
  * #29: Support for using tilde in source directory path to reference home directory.
  * Require "prefix" in retention section when "archive_name_format" is set. This is to avoid
-   accidental pruning of archives with a different archive name format.
+   accidental pruning of archives with a different archive name format. For similar reasons, default
+   "prefix" to "{hostname}-" if not specified.
  * Convert main source repository from Mercurial to Git.
  * Update dead links to Borg documentation.
 
diff --git a/borgmatic/borg/prune.py b/borgmatic/borg/prune.py
index 7f0c0381..0f20c3d6 100644
--- a/borgmatic/borg/prune.py
+++ b/borgmatic/borg/prune.py
@@ -19,6 +19,9 @@ def _make_prune_flags(retention_config):
             ('--keep-monthly', '6'),
         )
     '''
+    if not retention_config.get('prefix'):
+        retention_config['prefix'] = '{hostname}-'
+
     return (
         ('--' + option_name.replace('_', '-'), str(retention_config[option_name]))
         for option_name, value in retention_config.items()
diff --git a/borgmatic/config/schema.yaml b/borgmatic/config/schema.yaml
index 0c0a328d..c70cba09 100644
--- a/borgmatic/config/schema.yaml
+++ b/borgmatic/config/schema.yaml
@@ -132,7 +132,7 @@ map:
                 desc: |
                     When pruning, only consider archive names starting with this prefix.
                     Borg placeholders can be used. See the output of "borg help placeholders" for
-                    details.
+                    details. Default is "{hostname}-".
                 example: sourcehostname
     consistency:
         desc: |
diff --git a/borgmatic/tests/unit/borg/test_prune.py b/borgmatic/tests/unit/borg/test_prune.py
index 003b2cbb..ac941fea 100644
--- a/borgmatic/tests/unit/borg/test_prune.py
+++ b/borgmatic/tests/unit/borg/test_prune.py
@@ -18,7 +18,7 @@ BASE_PRUNE_FLAGS = (
 )
 
 
-def test_make_prune_flags_should_return_flags_from_config():
+def test_make_prune_flags_should_return_flags_from_config_plus_default_prefix():
     retention_config = OrderedDict(
         (
             ('keep_daily', 1),
@@ -29,7 +29,7 @@ def test_make_prune_flags_should_return_flags_from_config():
 
     result = module._make_prune_flags(retention_config)
 
-    assert tuple(result) == BASE_PRUNE_FLAGS
+    assert tuple(result) == BASE_PRUNE_FLAGS + (('--prefix', '{hostname}-'),)
 
 
 def test_make_prune_flags_accepts_prefix_with_placeholders():