Abs backup path (#108)

Author: demonolock

testgres/plugins/pg_probackup2/pg_probackup2/storage/fs_backup.py

@@ -43,7 +43,10 @@ class FSTestBackupDir(TestBackupDir):
     """ Backup directory. Usually created by running pg_probackup init -B <path>"""
 
     def __init__(self, *, rel_path, backup):
-        self.path = os.path.join(init_params.tmp_path, rel_path, backup)
+        backup_prefix = os.environ.get('PG_PROBACKUP_TEST_BACKUP_DIR_PREFIX')
+        if backup_prefix and not os.path.isabs(backup_prefix):
+            raise Exception(f"PG_PROBACKUP_TEST_BACKUP_DIR_PREFIX must be an absolute path, current value: {backup_prefix}")
+        self.path = os.path.join(backup_prefix or init_params.tmp_path, rel_path, backup)
         self.pb_args = ('-B', self.path)
 
     def list_instance_backups(self, instance):