The SpoolBuddy remote-update flow always pulled `main` on the remote
device when Bambuddy ran under Docker, regardless of which branch the
image was built from. Root cause: the Dockerfile COPYs only backend/
and static/, and .dockerignore excluded .git entirely, so the container
had no git metadata anywhere. detect_current_branch() silently fell
through its file-read path and returned the GIT_BRANCH env-var default
of "main".
The old subprocess-based implementation had the same bug but it was
masked twice: no .git in the image AND no `git` binary in the image,
so git rev-parse raised FileNotFoundError, the bare except swallowed
it, and the fallback kicked in.
Let the one file we actually need (.git/HEAD — ~20 bytes containing
`ref: refs/heads/<branch>`) through the .dockerignore filter and COPY
it into the image at /app/.git/HEAD. detect_current_branch() already
reads exactly that path, so no Python code changes are needed. Bind-
mount development setups are unaffected — the bind mount overlays the
baked-in file with the live repo's .git/HEAD.
Verified with a throwaway alpine build using the same .dockerignore
pattern: .git/HEAD passes through, decoy .git/refs and .git/objects
entries are excluded, and COPY writes the expected content into the
image.
maziggy