T289742: Extend zodbsync with an additional command zodbsync ff

perfact/zodbsync/commands/fastforward.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python
+
+from ..subcommand import SubCommand
+
+
+class FF(SubCommand):
+    '''
+    Perform a fast-forward merge to the target commit and apply changed paths
+    '''
+    @staticmethod
+    def add_args(parser):
+        parser.add_argument(
+            '--skip-errors', action='store_true', default=False,
+            help='Skip failed objects and continue',
+        )
+        parser.add_argument(
+            '--dry-run', action='store_true', default=False,
+            help='Only check for conflicts and roll back at the end.',
+        )
+        parser.add_argument(
+            'commit', type=str,
+            help='''Target commit'''
+        )
+
+    @SubCommand.gitexec
+    def run(self):
+        target = self.args.commit
+        self.logger.info('Attempting fast-forward merge to %s.' % target)
+        self.gitcmd_run('merge', '--ff-only', target)

perfact/zodbsync/main.py

@@ -28,14 +28,15 @@
 from .commands.freeze import Freeze
 from .commands.layer_init import LayerInit
 from .commands.layer_update import LayerUpdate
+from .commands.fastforward import FF
 
 
 class Runner(object):
     """
     Parses arguments to select the correct SubCommand subclass.
     """
     commands = [Record, Playback, Watch, Pick, Upload, WithLock, Reset, Exec,
-                Reformat, Checkout, Freeze, LayerInit, LayerUpdate]
+                Reformat, Checkout, Freeze, LayerInit, LayerUpdate, FF]
 
     def __init__(self):
         """

perfact/zodbsync/tests/test_sync.py

@@ -715,6 +715,29 @@ def test_watch_dump_setup(self):
                 tofind.remove(obj['path'])
         assert tofind == []
 
+    def test_ff(self):
+        """
+        Change the title on a second branch,
+        perform a fast-forward merge to it,
+        and verify that the change is correctly applied.
+        """
+        self.gitrun('checkout', '-b', 'second')
+        path = self.repo.path + '/__root__/index_html/__meta__'
+        with open(path) as f:
+            lines = f.readlines()
+        lines = [
+            line if "('title', " not in line
+            else "    ('title', 'test-ff'),\n"
+            for line in lines
+        ]
+        with open(path, 'w') as f:
+            f.writelines(lines)
+        self.gitrun('commit', '-a', '-m', 'Change title via ff')
+
+        self.gitrun('checkout', 'autotest')
+        self.run('ff', 'second')
+        assert self.app.index_html.title == 'test-ff'
+
     def test_reset(self):
         """
         Change the title of index_html in a second branch, reset to it and