diff --git a/routers/web/repo/compare.go b/routers/web/repo/compare.go
index e0855b1834843..f1b89a7be0d79 100644
--- a/routers/web/repo/compare.go
+++ b/routers/web/repo/compare.go
@@ -298,6 +298,13 @@ func ParseCompareInfo(ctx *context.Context) *CompareInfo {
 			ci.BaseBranch = baseCommit.ID.String()
 			ctx.Data["BaseBranch"] = ci.BaseBranch
 			baseIsCommit = true
+		} else if ci.BaseBranch == git.EmptySHA {
+			if isSameRepo {
+				ctx.Redirect(ctx.Repo.RepoLink + "/compare/" + util.PathEscapeSegments(ci.HeadBranch))
+			} else {
+				ctx.Redirect(ctx.Repo.RepoLink + "/compare/" + util.PathEscapeSegments(ci.HeadRepo.FullName()) + ":" + util.PathEscapeSegments(ci.HeadBranch))
+			}
+			return nil
 		} else {
 			ctx.NotFound("IsRefExist", nil)
 			return nil
diff --git a/services/repository/push.go b/services/repository/push.go
index 11854ccb3978c..b1dbe7d7f0e99 100644
--- a/services/repository/push.go
+++ b/services/repository/push.go
@@ -216,7 +216,34 @@ func pushUpdates(optsList []*repo_module.PushUpdateOptions) error {
 				if len(commits.Commits) > setting.UI.FeedMaxCommitNum {
 					commits.Commits = commits.Commits[:setting.UI.FeedMaxCommitNum]
 				}
-				commits.CompareURL = repo.ComposeCompareURL(opts.OldCommitID, opts.NewCommitID)
+
+				oldCommitID := opts.OldCommitID
+				if oldCommitID == git.EmptySHA && len(commits.Commits) > 0 {
+					oldCommit, err := gitRepo.GetCommit(commits.Commits[len(commits.Commits)-1].Sha1)
+					if err != nil && !git.IsErrNotExist(err) {
+						log.Error("unable to GetCommit %s from %-v: %v", oldCommitID, repo, err)
+					}
+					if oldCommit != nil {
+						for i := 0; i < oldCommit.ParentCount(); i++ {
+							commitID, _ := oldCommit.ParentID(i)
+							if !commitID.IsZero() {
+								oldCommitID = commitID.String()
+								break
+							}
+						}
+					}
+				}
+
+				if oldCommitID == git.EmptySHA && repo.DefaultBranch != branch {
+					oldCommitID = repo.DefaultBranch
+				}
+
+				if oldCommitID != git.EmptySHA {
+					commits.CompareURL = repo.ComposeCompareURL(oldCommitID, opts.NewCommitID)
+				} else {
+					commits.CompareURL = ""
+				}
+
 				notification.NotifyPushCommits(pusher, repo, opts, commits)
 
 				if err = models.RemoveDeletedBranchByName(repo.ID, branch); err != nil {