git-upstream-sync

name: git-upstream-sync description: Merge origin/main into the current branch and resolve conflicts, regenerating conflicted golden/generated files. Use when a PR has merge conflicts or the branch is behind origin/main.

Overview

Resolve GitHub PR conflicts by merging origin/main into the current branch.

Procedure

1. Fetch and merge with zdiff3

git fetch origin main
git -c merge.conflictstyle=zdiff3 merge origin/main

2. If conflicts exist, commit them as-is

If the merge produces conflicts, commit the conflict markers without resolving them first. This records the raw conflict state in a dedicated commit, separate from the resolution.

git add -A
git commit -m "merge origin/main (conflicts unresolved)"

3. Resolve conflicts

After committing the unresolved state:

1. Read each conflicted file and understand both sides of the conflict
2. Resolve conflicts in code files (remove conflict markers, choose correct code)
3. For generated files (golden fixtures, generated parsers, …) that conflict, regenerate them by re-running their generator and commit the fresh output — do not hand-resolve the markers or defer them (see "Generated files" below)
4. Stage and commit the resolution:

git add -A
git commit -m "resolve merge conflicts"

4. Run mise run test for sanity check

CI applies clippy and format, so a quick sanity check is sufficient.

Important

• Always use -c merge.conflictstyle=zdiff3 so the merge base is visible in conflict markers (with zealous zdiff3 reducing noise)
• Always commit the unresolved conflicts first, then resolve in a separate commit — this preserves a clear record of what the conflicts looked like vs how they were resolved
• Do NOT squash the two commits together

Generated files

• On a golden / generated-file conflict, always regenerate and commit. Re-run the generator (do not hand-resolve the markers) and commit its output. Do not skip them or defer them to on-task-done / CI.
• When there is no conflict, follow the task's explicit instruction for whether to regenerate. Regeneration is not always required; never let a generic "always regenerate" or "CI handles it" default override what you were asked to do.
• Never silently discard generated output (e.g. git restore to clean the tree or quiet a hook). Commit it, or ask. Discarding generated work without asking is always wrong.