Make SnapshotProvider more in line with reality

lib/tfw/components/snapshot_provider.py

@@ -1,6 +1,7 @@
 # Copyright (C) 2018 Avatao.com Innovative Learning Kft.
 # All Rights Reserved. See LICENSE file for details.
 
+import re
 from subprocess import run
 from getpass import getuser
 from os.path import isdir
@@ -21,16 +22,14 @@ class SnapshotProvider:
         }
 
         self._check_environment()
-
-        self._head_detached = False
-        self._branch = 'master'
-        self._branches = [self._branch]
-
+        self.__last_valid_branch = self._branch
         self._init_repo_if_needed()
 
     def _check_environment(self):
         if not isdir(self.gitenv['GIT_DIR']) or not isdir(self.gitenv['GIT_WORK_TREE']):
             raise EnvironmentError('Directories "directory" and "git_dir" must exist!')
+        if self._head_detached:
+            raise EnvironmentError(f'{self.__class__.__name__} cannot init from detached HEAD state!')
 
     def _init_repo_if_needed(self):
         if not self._repo_is_initialized():
@@ -51,9 +50,6 @@ class SnapshotProvider:
             'git', 'checkout',
             '-b', head_hash, head_hash
         ))
-        self._branches.append(head_hash)
-        self._branch = head_hash
-        self._head_detached = False
 
     def _get_head_hash(self):
         return self._get_stdout(('git', 'rev-parse', 'HEAD'))
@@ -61,7 +57,6 @@ class SnapshotProvider:
     def restore_snapshot(self, date):
         commit = self._get_commit_from_timestamp(date)
         self._checkout(commit)
-        self._head_detached = True
 
     def _get_commit_from_timestamp(self, date):
         return self._get_stdout((
@@ -69,7 +64,7 @@ class SnapshotProvider:
             '--date=iso',
             '-n', '1',
             f'--before="{date.isoformat()}"',
-            self._branch
+            self._last_valid_branch
         ))
 
     def _checkout(self, what):
@@ -93,10 +88,34 @@ class SnapshotProvider:
     def all_timelines(self):
         return self._branches
 
+    @property
+    def _branches(self):
+        git_branch_output = self._get_stdout(('git', 'branch'))
+        regex_pattern = re.compile(r'(?:[^\S\n]|[*])')  # matches '*' and non-newline whitespace chars
+        return re.sub(regex_pattern, '', git_branch_output).splitlines()
+
     @property
     def timeline(self):
         return self._branch
 
+    @property
+    def _branch(self):
+        return self._get_stdout((
+            'git', 'rev-parse',
+            '--abbrev-ref', 'HEAD'
+        ))
+
+    @property
+    def _last_valid_branch(self):
+        current_branch = self._branch
+        if current_branch != 'HEAD':
+            self.__last_valid_branch = current_branch
+        return self.__last_valid_branch
+
+    @property
+    def _head_detached(self):
+        return self._branch == 'HEAD'
+
     @timeline.setter
     def timeline(self, value):
         self._checkout(value)