dependabot: group mainly external repos (#2391)

Our own repos are mostly git depedencencies and often require manual
intervention. This is an attempt to split out updates of third party
depedencencies which are more likely to succeed without intervention.

.github/dependabot.yml

@@ -12,10 +12,32 @@ updates:
 
   - package-ecosystem: "cargo"
     directory: "/"
-    # Group all updates together
     groups:
+      # The `all` group should include mainly updates from crates.io which are
+      # more likely to succeed without intervention.
       all:
         patterns:
-        - "*"
+          - "*"
+        exclude-patterns:
+          - "ark-*"
+          - "cdn-*"
+          - "hotshot-*"
+          - "jf-*"
+          - "marketplace-*"
+      ark:
+        patterns:
+          - "ark-*"
+      cdn:
+        patterns:
+          - "cdn-*"
+      hotshot:
+        patterns:
+          - "hotshot-*"
+      jf:
+        patterns:
+          - "jf-*"
+      marketplace:
+        patterns:
+          - "marketplace-*"
     schedule:
       interval: "daily"