feat(datasource/maven): remove additional placeholders for scm.url (renovatebot#37332)

Co-authored-by: Michael Kriese <michael.kriese@gmx.de>

Author: phermsdorf

lib/modules/datasource/maven/__fixtures__/pom.scm-prefix.xml

@@ -11,7 +11,7 @@
   <name>Generic Package</name>
   <description>Generic Maven Package</description>
   <scm>
-    <url>scm:https://github.com/example/test</url>
+    <url>scm:https://github.com/example/test/tree/${project.scm.tag}</url>
     <connection>scm:git@github.com:example/test.git</connection>
     <developerConnection>scm:git@github.com:example/test.git</developerConnection>
   </scm>

lib/modules/datasource/maven/util.ts

@@ -276,6 +276,10 @@ function containsPlaceholder(str: string): boolean {
   return regEx(/\${.*?}/g).test(str);
 }
 
+function removeKnownPlaceholders(str: string): string {
+  return str.replace(regEx(/\/tree\/\${[^}]+}/), '');
+}
+
 export function getMavenUrl(
   dependency: MavenDependency,
   repoUrl: string,
@@ -454,7 +458,10 @@ export async function getDependencyInfo(
       }
 
       const sourceUrl = pomContent.valueWithPath('scm.url');
-      if (sourceUrl && !containsPlaceholder(sourceUrl)) {
+      if (
+        sourceUrl &&
+        !containsPlaceholder(removeKnownPlaceholders(sourceUrl))
+      ) {
         result.sourceUrl = sourceUrl
           .replace(regEx(/^scm:/), '')
           .replace(regEx(/^git:/), '')