kas: Support --update argument

By default we do not update a repository if the desired refspec is
already checked out and so we do not pull any new commits that may have
been added to this refspec upstream. If the new `--update` argument is
passed on the command line then we instead pull in any new upstream
commits.

Signed-off-by: Paul Barker <pbarker@konsulko.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/context.py

@@ -130,3 +130,7 @@ class Context:
     @property
     def force_checkout(self):
         return getattr(self.args, 'force_checkout', None)
+
+    @property
+    def update(self):
+        return getattr(self.args, 'update', None)

kas/kas.py

@@ -109,6 +109,10 @@ def setup_parser_common_args(parser):
     parser.add_argument('--force-checkout', action='store_true',
                         help='Always checkout the desired refspec of each '
                         'repository, discarding any local changes')
+    parser.add_argument('--update', action='store_true',
+                        help='Pull new upstream changes to the desired '
+                        'refspec even if it is already checked out locally')
+
 
 def kas_get_argparser():
     """

kas/repos.py

@@ -193,6 +193,7 @@ class RepoImpl(Repo):
         if self.refspec is None:
             return 0
 
+        if not get_context().update:
             # Does refspec exist in the current repository?
             (retc, output) = await run_cmd_async(self.contains_refspec_cmd(),
                                                  cwd=self.path,
@@ -203,7 +204,7 @@ class RepoImpl(Repo):
                              self.name, self.refspec, output.strip())
                 return retc
 
-        # No it is missing, try to fetch
+        # Try to fetch if refspec is missing or if --update argument was passed
         (retc, output) = await run_cmd_async(self.fetch_cmd(),
                                              cwd=self.path,
                                              fail=False)