Fix reset commit count after PR merge

Author: lafriks

models/pull.go

@@ -16,6 +16,7 @@ import (
 
 "code.gitea.io/git"
 "code.gitea.io/gitea/modules/base"
+"code.gitea.io/gitea/modules/cache"
 "code.gitea.io/gitea/modules/log"
 "code.gitea.io/gitea/modules/process"
 "code.gitea.io/gitea/modules/setting"
@@ -416,6 +417,9 @@ func (pr *PullRequest) Merge(doer *User, baseGitRepo *git.Repository, mergeStyle
 log.Error(4, "MergePullRequestAction [%d]: %v", pr.ID, err)
  }
 
+// Reset cached commit count
+cache.Remove(pr.Issue.Repo.GetCommitsCountCacheKey(pr.BaseBranch, true))
+
 // Reload pull request information.
 iferr=pr.LoadAttributes(); err!=nil{
 log.Error(4, "LoadAttributes: %v", err)