Subsequent backups against Gitea 1.24+ failed with the opaque
"Backup failed: 'tree'" message after the initial-backup fix landed in
7ee89b56. Root cause: Gitea's GET /repos/{owner}/{repo}/git/commits/{sha}
returns the wrapped Commit schema where the tree lives at
data["commit"]["tree"]["sha"], whereas GitHub's same-named Git Database
endpoint returns the unwrapped GitCommit schema with tree at the top
level. The bare commit_response.json()["tree"]["sha"] lookup at
gitea.py:109 raised KeyError: 'tree' and the broad except in push_files
surfaced it as the opaque "Backup failed: 'tree'" string — masking the
real shape mismatch.
Adds a _commit_tree_sha() helper that tries the flat shape first
(GitHub-compatible / older Gitea) and falls back to the wrapped shape
(Gitea 1.24+, Forgejo). Returns None on truly malformed responses;
push_files maps that to a clear "Failed to extract tree SHA from commit
response" instead of leaking a KeyError repr. Keeps the existing-files
diff working on both shapes so subsequent backups don't re-upload every
blob — preferred over the .get()-and-skip approach which would have
required also dropping base_tree from the tree POST and re-uploading
unchanged files on every backup.
maziggy
233808956b