Migration: only write commit-graph if wiki clone was successfull#19563

lunny merged 1 commit intogo-gitea:maingo-gitea/gitea:mainfrom

6543-forks:dont-write-commit-graph-on-non-existing-git-repo6543-forks/gitea:dont-write-commit-graph-on-non-existing-git-repoCopy head branch name to clipboard