Add smudge filter to replace $UNIXTIME directive on checkout

README.rst

@@ -15,6 +15,7 @@ Main features
 - check if zone file compiles properly using `named-compilezone(8)`_
 - autodetect zone name from file name or ``$ORIGIN`` directive
 - enforce updating serial number when zone content is changed
+- optional ``smudge`` filter to replace ``$UNIXTIME`` directive with current UNIX time
 - both ``pre-commit`` and ``pre-receive``/``update`` hooks to enforce similar checks in the remote repository
 - ``post-receive`` hook to checkout the working copy from a bare repository, generate config snippets for various DNS server software and reload them
 - only Python 3.5+ standard library is used
@@ -53,6 +54,29 @@ Full instalation and usage
   documentation on how to add custom hooks`_
 - on the server, set up the configuration options for each repository
 
+Support for $UNIXTIME directive
+-------------------------------
+
+If you want to use ``$UNIXTIME`` in your zone files instead of serial number,
+you have to install a `smudge` filter on the server, that will replace the
+directive with current unix time on checkout. First, set up the filter in
+the Git configuration:
+
+.. code-block:: shell
+
+        $ git config --global filter.dzonegit.smudge $(which dzonegit-smudge-serial)
+        $ git config --global filter.dzonegit.clean cat
+
+
+Then, apply the filter on all zone files using ``.gitattributes`` file inside
+the repository:
+
+.. code-block::
+
+        *.zone filter=dzonegit
+
+
+
 Configuration options
 ---------------------
 

dzonegit.py

@@ -509,6 +509,15 @@ def post_receive(stdin=sys.stdin):
                     subprocess.run(cmd)
 
 
+def smudge_serial(
+        bstdin=sys.stdin.buffer,
+        bstdout=sys.stdout.buffer,
+        unixtime=None,
+):
+    """Replace all $UNIXTIME directives with current unix time."""
+    bstdout.write(unixtime_directive(bstdin.read(), unixtime))
+
+
 def get_action(argv=sys.argv):
     name = Path(argv[0]).name
     if "pre-commit" in name:
@@ -519,6 +528,8 @@ def get_action(argv=sys.argv):
         return pre_receive
     if "post-receive" in name:
         return post_receive
+    if "smudge" in name:
+        return smudge_serial
 
 
 def main():

setup.py

@@ -23,6 +23,7 @@ setup(
                 "dzonegit-pre-receive = dzonegit:pre_receive",
                 "dzonegit-post-receive = dzonegit:post_receive",
                 "dzonegit-update = dzonegit:update",
+                "dzonegit-smudge-serial = dzonegit:smudge_serial",
             ],
     },
     classifiers=[

test_dzonegit.py

@@ -4,7 +4,7 @@ import subprocess
 import time
 import datetime
 import os
-from io import StringIO
+from io import StringIO, BytesIO
 from pathlib import Path
 
 import dzonegit
@@ -94,6 +94,13 @@ ns.example.com.      60 IN A 192.0.2.1
     assert r.serial == str(123456)
 
 
+def test_smudge_serial():
+    bstdin = BytesIO(b"something $UNIXTIME something")
+    bstdout = BytesIO()
+    dzonegit.smudge_serial(bstdin, bstdout, 123456)
+    assert b"something 123456 something" == bstdout.getvalue()
+
+
 def test_is_serial_increased():
     assert dzonegit.is_serial_increased(1234567890, "2018010100")
     assert dzonegit.is_serial_increased("2018010100", "4018010100")