Support layered config files

ghmoon

@@ -21,6 +21,15 @@ except:
 
 MIN_ENQUEUE_INTERVAL = 30
 
+def deep_merge(base, overlay):
+    """Recursively merge overlay into base. Dicts merge key-wise; everything else is replaced."""
+    if isinstance(base, dict) and isinstance(overlay, dict):
+        out = dict(base)
+        for k, v in overlay.items():
+            out[k] = deep_merge(base.get(k), v) if k in base else v
+        return out
+    return overlay
+
 gistgh = None
 context = None
 config = None
@@ -443,19 +452,20 @@ def init(args):
     global repos
     global wq
 
-    cfgfile = args.config
-    if not cfgfile:
+    cfgfiles = args.config
+    if not cfgfiles:
         for src in (os.path.expanduser("~/.ghmoon/config.yaml"),
                     "/etc/ghmoon/config.yaml"):
-            try:
-                cfgfile = open(src, "r")
+            if os.path.exists(src):
+                cfgfiles = [src]
                 break
-            except:
-                pass
 
-        assert cfgfile, "No config specified, an no default found"
+        assert cfgfiles, "No config specified, and no default found"
 
-    config = yaml.load(cfgfile, Loader=yaml.FullLoader)
+    config = {}
+    for path in cfgfiles:
+        with open(path, "r") as f:
+            config = deep_merge(config, yaml.load(f, Loader=yaml.FullLoader) or {})
     context = config.get("context", f"{getpass.getuser()}@{socket.gethostname()}")
 
     gistgh = GH(token=config.get("gist", {}).get("token"))
@@ -470,7 +480,8 @@ def init(args):
 if __name__ == "__main__":
     parser = argparse.ArgumentParser(prog="ghmoon")
     parser.add_argument("-f", "--config-file",
-                        type=argparse.FileType("r"), dest="config")
+                        action="append", dest="config", default=[],
+                        help="Config file (repeat to layer; later files override earlier ones)")
 
     sps = parser.add_subparsers(dest="cmd")