customManager for replacing latest tags.

default.json

@@ -48,6 +48,18 @@
     "dependencyDashboardApproval": true
   },
   "versioning": "docker",
+  "customManagers": [
+    {
+      "customType": "regex",
+      "fileMatch": ["docker-compose.yml"],
+      "matchStrings": [
+        "image: (?<depName>[^:]+):(?<currentValue>latest)"
+      ],
+      "datasourceTemplate": "docker",
+      "versioningTemplate": "docker",
+      "currentValueTemplate": "latest"
+    }
+  ],
   "packageRules": [
     {
       "description": "Alpine-based images only update to Alpine-based versions",
@@ -58,15 +70,9 @@
       "allowedVersions": "/alpine/i"
     },
     {
-      "description": "Replace :latest with semver tag + digest",
-      "matchDatasources": ["docker"],
-      "matchCurrentValue": "latest",
-      "versioning": "docker",
-      "pinDigests": true
-    },
-    {
-      "description": "Replace :stable with semver tag + digest",
+      "description": "Replace :stable with digest only",
       "matchDatasources": ["docker"],
+      "matchManagers": ["docker-compose"],
       "matchCurrentValue": "stable",
       "versioning": "docker",
       "pinDigests": true