Git Rerere

Git Rerere (Reuse Recorded Resolution)

Rerere fingerprints conflict hunks + resolutions. On any later merge/rebase/cherry-pick producing the same conflict, Git auto-applies the stored fix.

Enable

git config --global rerere.enabled true
git config --global rerere.autoupdate true   # also stage auto-resolved files

Storage: .git/rr-cache/<hash>/{preimage,postimage}. Local, not pushed.

Commands

git rerere status         # files with recorded preimages
git rerere diff           # current vs recorded resolution
git rerere remaining      # unresolved files
git rerere forget <file>  # discard a recorded resolution
git rerere gc             # prune old entries

Flow

1. First conflict: Recorded preimage for 'file'.
2. Resolve + commit: Recorded resolution for 'file'.
3. Next time the same conflict appears: Resolved 'file' using previous resolution. — with autoupdate, already staged.

Canonical Uses

• Long-running topic branch rebased onto main repeatedly.
• Nightly integration branches that merge many topics, reset, re-merge.
• Test-merge-and-reset to pre-record resolutions:

  git merge feature && git reset --hard HEAD~
  # resolution is recorded; next merge applies it automatically
  

Sharing

rr-cache isn't pushed. Copy between checkouts:

rsync -a .git/rr-cache/ other-repo/.git/rr-cache/

Pitfalls

• Matches exact conflict content — whitespace/ordering drift breaks the match. Check git rerere diff before trusting auto-resolution.
• With autoupdate=true, a bad past resolution silently re-applies. Spot-check.
• Auto-resolved files show no conflict markers; use git rerere forget <file> to re-surface for manual redo.