Gogs: UploadRepoFiles writes outside repo working tree via committed parent sym

Summary Repository.UploadRepoFiles checks for symlinks only on the leaf of the upload target osx.IsSymlinktargetPath. The siblings UpdateRepoFile, DeleteRepoFile, and GetDiffPreview use hasSymlinkInPath, which lstats every component — UploadRepoFiles is the lone outlier. An attacker with repo-wri...