fix(core): Fetch "extensionOf" branch state from the code system's...

...repository, not the one available from the context. The latter only
stores resource metadata and no branches outside MAIN exist in it.

core/com.b2international.snowowl.core/src/com/b2international/snowowl/core/codesystem/CodeSystemConverter.java

@@ -34,10 +34,7 @@
 import com.b2international.snowowl.core.version.Version;
 import com.b2international.snowowl.core.version.Versions;
 import com.google.common.base.Strings;
-import com.google.common.collect.Lists;
-import com.google.common.collect.Maps;
-import com.google.common.collect.Multimaps;
-import com.google.common.collect.TreeMultimap;
+import com.google.common.collect.*;
 
 /**
  * @since 7.6
@@ -80,8 +77,18 @@ private void expandExtensionOfBranchState(List<CodeSystem> results) {
 		}
 
 		// extensionOf branches are the parent branches of the CodeSystem, so simple branch state calculation is enough
-		BaseRevisionBranching branching = context().service(BaseRevisionBranching.class);
+		final RepositoryManager repositoryManager = context().service(RepositoryManager.class);
+		final Set<String> toolingIds = results.stream()
+			.map(CodeSystem::getToolingId)
+			.collect(Collectors.toSet());
+
+		final Map<String, BaseRevisionBranching> branchingMap = toolingIds.stream()
+			.collect(ImmutableMap.toImmutableMap(
+				id -> id, 
+				id -> repositoryManager.get(id).service(BaseRevisionBranching.class)));
+
 		for (CodeSystem result : results) {
+			BaseRevisionBranching branching = branchingMap.get(result.getToolingId());
 			RevisionBranch branch = branching.getBranch(result.getBranchPath());
 			BranchState branchState = branching.getBranchState(branch);
 			result.setExtensionOfBranchInfo(new BranchInfo(branch.getPath(), branchState, branch.getBaseTimestamp(), branch.getHeadTimestamp()));