safe-pull-and-rollback

name	safe-pull-and-rollback
description	Tag-before-pull pattern with diff, rollback, and cross-machine sharing. Use when the user is about to pull from origin and wants a safety net, or wants to compare what's about to land, or wants to revert after a pull broke something.

Safe pull / rollback / compare

The drone-follow branch (hailo_drone_follow) tends to drift far ahead of local checkouts (we've seen 28-commit-ahead pulls touching 23 files). Always tag before fast-forwarding so you can A/B test and roll back.

Tag the current tip

TAG="pre-pull-hailo_drone_follow-$(date +%Y%m%d)"
git tag -a "$TAG" -m "Local hailo_drone_follow tip before pulling from origin"
git rev-parse "$TAG^{commit}"   # confirm it points at HEAD

Use an annotated tag (-a), not a lightweight tag — annotated tags carry a message, push cleanly, and survive git gc better.

Inspect what's about to land

git fetch --quiet
git log HEAD..origin/hailo_drone_follow --oneline                # commit list
git diff --stat HEAD..origin/hailo_drone_follow | head -30       # file-level
git diff --stat HEAD..origin/hailo_drone_follow -- \
  community/apps/hailo_drone_follow/drone_follow/pipeline_adapter/   # tracking files only

For a deeper read on tracking-affecting changes, see ../../memory/tracking_callback_risks.md.

Pull

git pull --ff-only          # refuse if not fast-forwardable

Fast-forward only — if it can't, your local has commits the remote doesn't and you should rebase or merge deliberately.

Diff against the saved tag (post-pull)

git diff <TAG>..HEAD                                    # full diff
git diff <TAG>..HEAD -- <path>                          # scoped
git log <TAG>..HEAD --oneline                           # commits since tag

Roll back

git reset --hard <TAG>           # local branch rewinds to tag
# untracked files survive a hard reset; only tracked files are reset

Or, to look around without moving the branch:

git checkout <TAG>               # detached HEAD
# ...inspect, run...
git switch -                     # back to previous branch

Push the tag (so other machines / the air unit can use it)

git push origin <TAG>
git ls-remote --tags origin <TAG>    # verify

On the other machine:

git fetch --tags origin
git checkout <TAG>                       # detached HEAD
git switch -c pre-pull-test <TAG>        # or a branch

When you have uncommitted changes

A simple git checkout <other-branch> works only if the files you've modified have identical content on both branches. Otherwise:

• Tracked-file changes against a divergent base ⇒ stash first: git stash --include-untracked.
• Untracked files always travel with checkout — no stash needed for them.

Don'ts

• Don't git pull (without --ff-only) when behind — it'll merge and create a noisy commit.
• Don't git reset --hard without first verifying the tag exists: git rev-parse <TAG>.
• Don't push tags to origin before confirming the user wants them shared. Tags pushed accidentally are awkward to remove (git push origin :refs/tags/<TAG> is the cleanup but takes a round-trip).