/prepare-merge — Clean up a feature branch before merging to dev

Rebase the current feature branch onto origin/dev, regroup its commits into a history worth keeping, and drop this branch's superpowers working docs — so dev history records the work, not the fix trail.

How much to squash is the user's call, not yours. The skill works out the branch's real concerns, presents up to three plans — Perfect, Medium, Min. commits — and builds whichever one the user picks. There is no default commit count and no target to squash down to.

User-invocable

When the user types /prepare-merge, run this skill.

Preconditions (abort and tell the user if violated)

• Current branch is a feature branch — not dev, master, or release/*.
• Working tree is clean (git status --short empty).
• git fetch origin dev succeeded.

Steps

1. Safety backup

git branch <branch-name>-bak HEAD

Never rewrite history without this. If <branch-name>-bak already exists from a previous run, keep it as-is — it points at the true original, and overwriting it with already-rewritten history would defeat the backup.

2. Rebase onto origin/dev

git rebase origin/dev (skip if already based on its tip). On conflicts, resolve preserving both sides' intent and GIT_EDITOR=true git rebase --continue; if a resolution is not obvious from the code, git rebase --abort and ask the user. Interactive git (git rebase -i with an editor, git add -p/-i) hangs in this environment — never use it.

Then capture the parity baseline: REBASED=$(git rev-parse HEAD).

3. Plan the commit structure — always offer the choice

Read git log --oneline origin/dev..HEAD and the full diff git diff origin/dev..HEAD, and work out what genuinely distinct concerns the branch holds — separate features, separate fixes, infrastructure the feature merely builds on.

That list of concerns is the input to the three plans below. Deciding on a structure yourself and presenting it as "the plan" is the one thing this step must not do — the plans are cheap to draw up, and which trade-off is right depends on how the user wants this branch to read in dev history.

Original commit boundaries are not the answer: fix/review-comment commits always fold into what they fix, and several commits on one concern fold together. But never merge two unrelated concerns just to get the count down — a smaller history is not the goal, an honest one is.

Split at whatever granularity gives the cleanest history, including within a single file: a file touched by two concerns gets its hunks split between them. git add -p hangs in this environment, so stage hunks through a patch instead:

git diff <base> HEAD -- <file> > tmp/f.patch   # then trim it to the wanted hunks
git apply --cached tmp/f.patch

Then offer the user up to three plans and let them choose:

Plan	What it does
Perfect	One commit per distinct concern. Nothing unrelated is ever squashed together. The most commits, and the most faithful history. This can come out identical to the branch's existing history — if the commits already map one-to-one onto the concerns, Perfect means "leave the splits alone", and say so rather than inventing a regrouping.
Medium	Each real feature keeps its own commit, but secondary work is consolidated — all the small fixes into one fix(...), all the docs into one docs(...), and so on.
Min. commits	Aggressively minimal, typically ≤3: the whole feature as one commit, plus only those concerns that genuinely could not ride along with it.

Offer only the plans that actually differ for this branch — a single-concern branch collapses all three into the same one commit, and then there is nothing to ask. Present each plan as its list of commit messages so they can be compared, ask which to use, and build that one. Label Perfect as "unchanged" when it reproduces the current history, so the user can see that one of the options is to keep what is already there.

Messages follow repo convention: type(scope): summary, scopes as used on this branch and recent dev history; when folding several commits loses important detail, keep the summary line and add a short body naming what was folded in.

4. Identify superpowers docs to drop

git diff --diff-filter=A --name-only $(git merge-base HEAD origin/dev) HEAD -- docs/superpowers/

Only files added by this branch are deleted — plans and specs are working documents that die when the feature ships. Pre-existing files under docs/superpowers/, including ones this branch merely modified, are living docs and stay untouched.

5. Squash

If the chosen plan reproduces the branch's existing history and step 4 found no docs to drop, there is nothing to rewrite: skip to step 6, and tell the user the history was already right. Otherwise the mixed reset below rebuilds it — that is also how the superpowers docs get stripped out of history rather than deleted in a trailing commit.

git reset --mixed $(git merge-base HEAD origin/dev)
rm <files from step 4>
# then per planned group:
git add <group paths> && git commit -m "type(scope): summary"

Every change must belong to exactly one group before you start — a file split across groups is staged hunk-by-hunk via git apply --cached, as in step 3. After the last commit git status --short must be empty.

6. Verify (mandatory before claiming done)

• git branch --show-current → still the feature branch. A git rebase --onto given a non-branch revision (like HEAD~0) rebases a detached HEAD and leaves the branch ref behind — later steps would then rewrite and push a stale tip. If detached, repoint: git branch -f <branch> <verified-tip> and check it out.
• git status --short → empty.
• git diff $REBASED HEAD → shows only the step-4 doc deletions. Compare against the post-rebase tip, not the backup branch — the backup predates the rebase, so diffing it mixes in upstream changes.
• Show git log --oneline origin/dev..HEAD to the user.

7. Confirm, then push with the remote backup

Show the user the final commit list and the deleted doc files, and ask whether the new history is fine. Do not push anything before that confirmation. Once the user confirms:

git push origin <branch-name>-bak
git push --force-with-lease origin <branch-name>

The backup goes up first — with the pre-rewrite history on origin, no outcome of the force-push can lose code, and anyone can check the old branch out from the remote. Afterwards verify the branch tracks its remote cleanly (git status shows "up to date with origin/").

Report both pushed refs and remind the user to delete the backup after the merge lands: git branch -D <branch-name>-bak && git push origin :<branch-name>-bak.

Common mistakes

Mistake	Fix
Rewriting with no backup ref	Step 1 first, always
Parity-diffing against the backup branch	Use $REBASED (post-rebase tip)
Deleting pre-existing docs/superpowers/ files	Only --diff-filter=A files from this branch
git rebase -i / git add -p	They hang here; mixed-reset + regroup, and git apply --cached for hunks
One commit per original "meaningful" commit	Boundaries come from the concerns in the diff, not from the old history
Squashing unrelated concerns to hit a lower count	Only the plan the user picked decides how much gets folded
Building a plan without offering the alternatives	Present Perfect / Medium / Min. commits and let the user choose
Regrouping a history that was already correct	Perfect may well be "unchanged" — offer it as such
Pushing before the user confirms the result	Ask first; then -bak goes up before the force-push
Overwriting an existing -bak on a rerun	It holds the true original; leave it untouched