documenting how to get a list of documents with default_branch (name) and default_branch_protection

otterdog_database/doc/HOWTO.md

@@ -137,4 +137,76 @@ db.branch_security_rules.aggregate([
 
 
 
-```
\ No newline at end of file
+```
+
+## How to get a list of documents with default_branch (name) and default_branch_protection
+
+* Local instance
+TBD
+
+* Free MongoDB cloud instance
+
+```javascript
+db.getCollection("branch_security_rules").aggregate([{
+    $project:{
+        _id:0,
+        github_id: 1,
+      repositories: {
+          $map:{
+              input: "$repositories",
+              as: "repo",
+              in: {
+                  repo_name: "$$repo.name",
+                  repo_default_branch: "$$repo.default_branch",
+                  branch_protection_rules: "$$repo.branch_protection_rules",
+              }
+          }
+      },
+    }
+}, {
+    $unwind: "$repositories"
+},{
+    $project:{
+        _id:0,
+        github_id: 1,
+        repo_name: "$repositories.repo_name",
+        repo_default_branch: "$repositories.repo_default_branch",
+        repo_branch_protection_rules: "$repositories.branch_protection_rules",
+
+    }
+}, {
+    $sort: {
+        total_repo_branch_protection_rules: -1
+    }
+}, {
+    $project: {
+        _id:0,
+        github_id: 1,
+        repo_name: 1,
+        repo_default_branch: 1,
+        repo_branch_protection_rules: {
+            $filter: {
+                input: "$repo_branch_protection_rules",
+                as: "bpr",
+                cond: { $eq: ["$$bpr.pattern", "$repo_default_branch"] }
+            }
+        }
+    }
+},{
+    $project: {
+        _id:0,
+        github_id: 1,
+        repo_name: 1,
+        repo_default_branch: 1,
+        repo_default_branch_protection: {
+            $cond: {
+                if: { $eq: [ "$repo_branch_protection_rules", []]},
+                then: "not protected",
+                else: "protected"
+            }
+        }
+    }
+}
+])
+
+```