default-reviewers: handle no common ancestor case.

rhodecode/apps/repository/views/repo_review_rules.py

@@ -72,6 +72,7 b' class RepoReviewRulesView(RepoAppView):'
         target_type = request.GET['target_ref_type']
         target_name = request.GET['target_ref_name']
 
+        try:
         review_data = get_default_reviewers_data(
             current_user,
             source_repo,
@@ -79,4 +80,10 b' class RepoReviewRulesView(RepoAppView):'
             target_repo,
             Reference(target_type, target_name, target_commit_id)
         )
+        except ValueError:
+            # No common ancestor
+            msg = "No Common ancestor found between target and source reference"
+            log.exception(msg)
+            return {'diff_info': {'error': msg}}
+
         return review_data

rhodecode/public/js/src/rhodecode/pullrequests.js

@@ -332,7 +332,10 b' window.ReviewersController = function ()'
 
                 // review rules
                 self.loadReviewRules(data);
-                self.handleDiffData(data["diff_info"]);
+                var diffHandled = self.handleDiffData(data["diff_info"]);
+                if (diffHandled === false) {
+                    return
+                }
 
                 for (var i = 0; i < data.reviewers.length; i++) {
                     var reviewer = data.reviewers[i];
@@ -473,7 +476,7 b' window.ReviewersController = function ()'
     };
 
     this.handleDiffData = function (data) {
-        self.diffDataHandler(data)
+        return self.diffDataHandler(data)
     }
 };
 

rhodecode/templates/pullrequests/pullrequest.mako

@@ -309,6 +309,13 b''
    var codeMirrorInstance = $('#pullrequest_desc').get(0).MarkupForm.cm;
 
    var diffDataHandler = function(data) {
+       if (data['error'] !== undefined) {
+           var noCommitsMsg = '<span class="alert-text-error">{0}</span>'.format(data['error']);
+           prButtonLock(true, noCommitsMsg, 'compare');
+           //make both panels equal
+           $('.target-panel').height($('.source-panel').height())
+           return false
+       }
 
        var commitElements = data['commits'];
        var files = data['files'];
@@ -395,7 +402,8 b''
        }
 
        //make both panels equal
-       $('.target-panel').height($('.source-panel').height())
+       $('.target-panel').height($('.source-panel').height());
+       return true
    };
 
    reviewersController = new ReviewersController();