Hide build buttons in Multibranch branch/PR jobs when the Multibranch or organization folder is disabled (#26131)

Author: mawinter69

core/src/main/java/hudson/model/Build.java

@@ -83,7 +83,7 @@
  *
  * @author Kohsuke Kawaguchi
  */
-public abstract class Build<P extends Project<P, B>, B extends Build<P, B>>
+public abstract class   Build<P extends Project<P, B>, B extends Build<P, B>>
     extends AbstractBuild<P, B> {
 
     /**

core/src/main/java/hudson/model/BuildableItem.java

@@ -57,4 +57,14 @@ default boolean scheduleBuild(int quietPeriod) {
     }
 
     boolean scheduleBuild(int quietPeriod, Cause c);
+
+    /**
+     * Whether the item is buildable.
+     *
+     * @return true, if the item can be built.
+     * @since TODO
+     */
+    default boolean isBuildable() {
+        return true;
+    }
 }

core/src/main/java/jenkins/model/ParameterizedJobMixIn.java

@@ -40,6 +40,7 @@
 import hudson.model.Cause;
 import hudson.model.CauseAction;
 import hudson.model.Item;
+import hudson.model.ItemGroup;
 import hudson.model.Items;
 import hudson.model.Job;
 import hudson.model.ParameterDefinition;
@@ -562,8 +563,17 @@ default RunT createExecutable() throws IOException {
             return null;
         }
 
+        @Override
         default boolean isBuildable() {
-            return !isDisabled() && !((Job) this).isHoldOffBuildUntilSave();
+            if (isDisabled() || ((Job) this).isHoldOffBuildUntilSave()) {
+                return false;
+            }
+            // If parent is disabled, child jobs (e.g., branch jobs) should not be buildable
+            ItemGroup<? extends Item> parentGroup = ((Job) this).getParent();
+            if (parentGroup instanceof BuildableItem bi) {
+                return bi.isBuildable();
+            }
+            return true;
         }
 
         @Extension