teuthology/suite: merge base_config with other fragments

Presently the code tries to merge the base_config when the worker starts
running. There's no need to construct it this way and it prevents sharing the
"defaults" with the fragment merging infrastructure. It also prevents
overriding defaults like:

    kernel
        branch: wip-pdonnell-i66704
        client:
            branch: wip-pdonnell-i66704
            flavor: default
            kdb: 1
            sha1: 745cacd8f31e50d7f3b6039bbd8c9a8dfc07bf03
        flavor: default
        kdb: 1
        sha1: 745cacd8f31e50d7f3b6039bbd8c9a8dfc07bf03

A YAML fragment set kernel.client but it cannot delete the changes to
kernel.(branch|flavor|kdb|sha1) because there's no way to remove YAML elements
via a deep merge.

Signed-off-by: Patrick Donnelly <[email protected]>

teuthology/suite/merge.py

@@ -1,4 +1,5 @@
 import copy
+import itertools
 import logging
 import lupa
 import os
@@ -115,13 +116,15 @@ def config_merge(configs, suite_name=None, **kwargs):
     the entire job (config) from the list.
     """
     seed = kwargs.setdefault('seed', 1)
+    base_config = kwargs.setdefault('base_config', {})
     if not isinstance(seed, int):
         log.debug("no valid seed input: using 1")
         seed = 1
     log.debug("configuring Lua randomseed to %d", seed)
     L.execute(f'local math = require"math"; math.randomseed({seed});')
     new_script = L.eval('new_script')
-    yaml_cache = {}
+    base_config_path = '\0' # not a valid path
+    yaml_cache = {base_config_path: base_config}
     for desc, paths in configs:
         log.debug("merging config %s", desc)
 
@@ -130,7 +133,7 @@ def config_merge(configs, suite_name=None, **kwargs):
 
         yaml_complete_obj = {}
         deep_merge(yaml_complete_obj, dict(TEUTHOLOGY_TEMPLATE))
-        for path in paths:
+        for path in itertools.chain((base_config_path,), paths):
             if path not in yaml_cache:
                 with open(path) as f:
                     txt = f.read()

teuthology/suite/run.py

@@ -514,7 +514,6 @@ def collect_jobs(self, arch, configs, newest=False, limit=0):
                 '--description', description,
                 '--',
             ])
-            arg.extend(self.base_yaml_paths)
 
             parsed_yaml_txt = yaml.dump(parsed_yaml)
             arg.append('-')