Implement git based fs snapshot provider

lib/tfw/components/__init__.py

@@ -9,3 +9,4 @@ from .history_monitor import HistoryMonitor, BashMonitor, GDBMonitor
 from .terminal_commands import TerminalCommands
 from .log_monitoring_event_handler import LogMonitoringEventHandler
 from .fsm_managing_event_handler import FSMManagingEventHandler
+from .snapshot_provider import SnapshotProvider

lib/tfw/components/snapshot_provider.py

@@ -0,0 +1,54 @@
+# Copyright (C) 2018 Avatao.com Innovative Learning Kft.
+# All Rights Reserved. See LICENSE file for details.
+
+from subprocess import run
+from getpass import getuser
+
+
+class SnapshotProvider:
+    def __init__(self, directory, git_dir):
+        author = f'{getuser()} via TFW {self.__class__.__name__}'
+        self.gitenv = {
+            'GIT_DIR': git_dir,
+            'GIT_WORK_TREE': directory,
+            'GIT_AUTHOR_NAME': author,
+            'GIT_AUTHOR_EMAIL': '',
+            'GIT_COMMITTER_NAME': author,
+            'GIT_COMMITTER_EMAIL': ''
+        }
+
+    def init_repo(self):
+        self._run(('git', 'init'))
+
+    def take_snapshot(self):
+        self._run(('git', 'add', '-A'))
+        self._run(('git', 'commit', '-m', 'Snapshot'))
+
+    def restore_snapshot(self, date):
+        commit = self._get_commit_from_timestamp(date)
+        self._checkout_commit(commit)
+
+    def _get_commit_from_timestamp(self, date):
+        return self._get_stdout((
+            'git', 'rev-list',
+            '--date=iso',
+            '-n', '1',
+            f'--before="{date.isoformat()}"',
+            'master'
+        ))
+
+    def _checkout_commit(self, commit):
+        self._run((
+            'git', 'checkout',
+            commit
+        ))
+
+    def _get_stdout(self, *args, **kwargs):
+        kwargs['capture_output'] = True
+        stdout_bytes = self._run(*args, **kwargs).stdout
+        return stdout_bytes.decode().rstrip('\n')
+
+    def _run(self, *args, **kwargs):
+        if 'env' not in kwargs:
+            kwargs['env'] = self.gitenv
+        return run(*args, **kwargs)