add support for lockfiles on checkout

When checking out repositories, check if a file <filename>.lock.<ext>
exists next to the file specified first on the kas CLI. In case this
file exists and the --update option is not specified, automatically
append this file to the kas CLI before performing any other kas
operations.

When --update is specified, the lockfile is ignored.

Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/config.py

@@ -58,7 +58,11 @@ class Config:
                                    'belong to the same repository or all '
                                    'must be outside of versioning control')
 
-        self.handler = IncludeHandler(self.filenames, self.top_repo_path)
+        update = ctx.args.update if hasattr(ctx.args, 'update') else False
+
+        self.handler = IncludeHandler(self.filenames,
+                                      self.top_repo_path,
+                                      not update)
         self.repo_dict = self._get_repo_dict()
 
     def get_build_system(self):

kas/includehandler.py

@@ -26,6 +26,7 @@
 """
 
 import os
+from pathlib import Path
 from collections import OrderedDict
 from collections.abc import Mapping
 import functools
@@ -121,12 +122,26 @@ class IncludeHandler:
         relative to the repository root path.
 
         The includes are read and merged from the deepest level upwards.
+
+        In case ignore_lock is false, kas checks if a file <file>.lock.<ext>
+        exists next to the first entry in top_files. This file is then appended
+        to the list of top_files.
     """
 
-    def __init__(self, top_files, top_repo_path):
+    def __init__(self, top_files, top_repo_path, use_lock=True):
         self.top_files = top_files
         self.top_repo_path = top_repo_path
 
+        if use_lock:
+            lockfile = self.get_lockfile()
+            if Path(lockfile).exists():
+                logging.debug('includehandler: append lockfile %s', lockfile)
+                self.top_files.append(lockfile)
+
+    def get_lockfile(self):
+        file = Path(self.top_files[0])
+        return file.parent / (file.stem + '.lock' + file.suffix)
+
     def get_config(self, repos=None):
         """
         Parameters: