cloud-native-ref: Skill for Claude Code

Sync branch onto origin/main

A branch that is behind origin/main produces a diff that no longer describes what will merge. Reviews read the wrong merge base, CI passes against code nobody will ship, and conflicts surface at merge time instead of now.

Run this before every review, push and PR — not only when a conflict is suspected.

1. Refuse the unsafe cases

Stop and report, do not proceed, when any of these hold:

Condition	Check	Why
On the base branch itself	git branch --show-current is main	nothing to rebase
Uncommitted changes	git status --porcelain is non-empty	a rebase would strand them. Commit first — ship-it does this before calling you
Rebase already running	test -d "$(git rev-parse --git-path rebase-merge)", same for rebase-apply	finish or abort it first

Resolve that third one through git rev-parse --git-path, never as a literal .git/…. In a worktree .git is a file, not a directory — it holds gitdir: …/.git/worktrees/<name> — so a literal path can never match and the guard silently passes. This repo mandates a worktree for every change, which would make the check dead everywhere it matters.

2. Fetch, then compare

The fetch is the point. Comparing against a local origin/main that was last updated hours ago reports "up to date" on a branch that is not.

BASE="${BASE:-main}"
git fetch origin "$BASE"

if git merge-base --is-ancestor "origin/$BASE" HEAD; then
  echo "up to date with origin/$BASE"
else
  echo "behind origin/$BASE by $(git rev-list --count HEAD..origin/$BASE) commit(s)"
fi

When the branch is already up to date, say so and stop. Do not rebase for the sake of it — a no-op rebase still rewrites committer dates and invalidates anyone's local copy.

3. Rebase

git rebase "origin/$BASE"

On conflict, resolve one file at a time and preserve intent from both sides:

git status --short | grep '^UU'   # conflicted files
# edit, then:
git add <file>
git rebase --continue