context: Provide global instance

This will avoid the increasingly ugly pushing around of a context
instance as parameter to various methods/functions. Everyone can now
simply call get_context() after build or shell called
create_global_context().

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/build.py

@@ -24,7 +24,7 @@
 """
 
 import os
-from .context import Context
+from .context import create_global_context
 from .libkas import find_program, run_cmd, kasplugin
 from .libcmds import (Macro, Command, SetupDir, CleanupSSHAgent,
                       SetupSSHAgent, SetupEnviron, SetupRepos,
@@ -71,7 +71,7 @@ class Build:
         if args.cmd != 'build':
             return False
 
-        ctx = Context(args.config, args.target, args.task)
+        ctx = create_global_context(args.config, args.target, args.task)
 
         macro = Macro()