Add attribute visit_type.

Will be required by swh-loader-core v0.0.45.

swh/loader/git/from_disk.py

@@ -23,6 +23,8 @@ class GitLoaderFromDisk(UnbufferedLoader):
 
     CONFIG_BASE_FILENAME = 'loader/git-disk'
 
+    visit_type = 'git'
+
     def __init__(self, config=None):
         super().__init__(logging_class='swh.loader.git.Loader', config=config)
 

swh/loader/git/loader.py

@@ -192,6 +192,8 @@ class GitLoader(UnbufferedLoader):
         'pack_size_bytes': ('int', 4 * 1024 * 1024 * 1024),
     }
 
+    visit_type = 'git'
+
     def __init__(self, repo_representation=RepoRepresentation, config=None):
         """Initialize the bulk updater.