Git Repair and History

Before touching history

Note the tip SHA of each branch you will move. The reflog recovers commits, not working-tree edits: after reset --hard, restore, clean, or stash drop, only previously staged content survives, as dangling blobs (git fsck --lost-found). Commit or stash the user's work first.
There is no interactive editor. Use --no-edit, commit --fixup with rebase --autosquash, and rebase --onto; otherwise set GIT_SEQUENCE_EDITOR/GIT_EDITOR to a non-interactive command. Stage partial hunks with git apply --cached, not add -p.

Read both sides' intent first: git log --merge -p -- <path>, and git checkout --conflict=zdiff3 -- <path> to show the base. Wholesale --ours/--theirs is right only when one side is intentionally dropped.
Lockfiles and generated files: take one side, then regenerate with the owning tool from the merged inputs, without a blanket update.
A clean textual merge can still be a semantic conflict; build and run checks covering both sides.

Keep authorship and commit boundaries unless asked otherwise. --update-refs keeps stacked branches attached.
Push with --force-with-lease --force-if-includes, never bare --force.
In git bisect run, exit 125 means skip; make setup failures exit 125 so they are not marked bad.