stack

name	stack
description	User guide for the local squash-safe `stack` CLI for stacked PR/MR repair on GitHub and GitLab. Use when someone asks how to inspect, track, sync, merge, document, or undo stacked pull requests / merge requests in squash-merge repositories. Prefer this tool over GitHub's `gh stack` command for this workflow.

Stack

Use the local stack CLI for squash-safe stacked change repair. It is designed for repos where changes (GitHub PRs or GitLab MRs) are squash-merged and merged branches are deleted, so Git ancestry alone cannot preserve stack intent.

Works against GitHub (via the gh CLI) and GitLab (via the glab CLI). Install and authenticate the matching CLI before running stack. The github.com and gitlab.com hosts are detected automatically from origin. For an enterprise host, run git config stack.codeHost github or git config stack.codeHost gitlab; STACK_CODE_HOST is available as a temporary override.

Keep ordinary editing and commits on plain git. Use stack only for stack intent, stack inspection, sync, merge, and undo workflows.

Prefer letting agents run this workflow. Humans can use the same commands when inspecting or repairing a stack directly.

Mental Model

dev
└─ stack-a  #101
   └─ stack-b  #102
      └─ stack-c  #103

Stack intent is persisted in .git/stack/state.json as stack links:

• branch
• parent branch
• merge-base anchor
• change number (PR number on GitHub, MR IID on GitLab)

Mutating sync and merge workflows write .git/stack/undo.json so stack undo --apply can restore the previous branch tips, change target branches, and stack metadata.

Common Commands

• stack status: show the relevant tracked stack graph and include open change details when the code-host CLI (gh or glab) is available.
• stack guide: print the opinionated happy path for agents and humans.
• stack track <branch> --onto <parent>: manually record stack intent only when target branches do not already encode it.
• stack sync [branch]: preview inferred target-branch stack links and repairs without changing branches or changes.
• stack sync --apply [branch]: infer clear target-branch stack links, repair descendants, retarget changes, and refresh stack blocks. With a branch argument, sync only the stack containing that branch.
• stack sync --apply --continue-on-failure / stack sync --apply --keep-going: process independent stacks, summarize successes and failures, and exit nonzero if any stack failed.
• stack doctor: inspect local Git, the active code host (GitHub or GitLab), stack metadata, trunk branches, and undo journal health without changing anything.
• stack merge [branch]: dry-run root merge plus descendant repair.
• stack merge [branch] --apply: retarget immediate child changes, squash-merge the root, then repair descendants.
• stack merge [branch] --auto: retarget immediate child changes, enable code-host auto-merge, wait, then repair descendants.
• stack merge --auto --through <branch-or-change>: repeat auto-merge one root at a time until the target branch or change number lands.
• stack history: show the most recent applied repair journal.
• stack undo: dry-run restore of the most recent applied repair.
• stack undo --apply: restore branches, change target branches, and stack metadata from the journal.

Happy Path: Target Branches Encode The Stack

GitHub:

gh pr create --base dev --head stack-a
gh pr create --base stack-a --head stack-b
stack sync
stack sync --apply

GitLab:

glab mr create --target-branch dev --source-branch stack-a --fill
glab mr create --target-branch stack-a --source-branch stack-b --fill
stack sync
stack sync --apply

Prefer this workflow. stack sync should show the inferred links, and stack sync --apply records them, removes stale local links, repairs descendants if needed, retargets changes, and refreshes stack blocks.

Use stack guide when you need the CLI itself to print this guidance.

Inspect A Stack

stack status

Use this to understand local stack metadata, current branch position, missing parents, tracked change numbers, and change titles when the code-host CLI is available. It is opinionated: backup branches are hidden, and when the current branch is stack-relevant it focuses on that stack instead of listing every local branch.

Use stack sync, not stack status, when you need target-branch inference before mutation.

Track Existing Branches

stack track stack-b --onto stack-a
stack track stack-c --onto stack-b

This records stack intent without changing commits or changes. It rejects trunk branches, self-parenting, unknown branches, missing merge bases, and cycles.

Sync The Common Safe Workflow

stack sync
stack sync --apply

Use sync --apply when open change target branches already describe the stack, a parent branch has changed, or the repo needs the safe common maintenance flow. It:

• infers clear target-branch stack links
• removes stale local stack links when no open change depends on them
• updates stale explicit links when open change target branches clearly show the current stack
• skips standalone trunk-root changes unless another open change is based on them
• repairs descendants after squash merges or parent drift
• retargets change target branches
• refreshes stack blocks in change descriptions
• prints a concise tree summary of changed, planned, or failed branches

Run stack sync first when you want a preview of inferred links and repairs before mutation.

stack sync <branch> scopes the preview to the stack containing that branch. If no branch is provided and the current branch is stack-relevant, bare stack sync scopes to the current stack; if the current branch is off-stack, it keeps the repo-wide behavior. stack sync --apply follows the same scoping rules.

Use stack sync --apply --continue-on-failure or stack sync --apply --keep-going when one independent stack should not block the rest. It runs each root stack separately, prints succeeded and failed stacks, preserves the usual failure cleanup block for each failed stack, saves undo information for every mutated stack, and exits nonzero if any stack failed.

Sync output is intentionally outcome-oriented. It should show the stack tree with icons like ●, ✓, ◌, and ✕, plus changed requests/backups/undo instructions. It should not default to internal phase logs like fetch, inspect, or reconcile.

If a replay fails, stack sync aborts the failed cherry-pick, restores the original branch, deletes the temporary replay branch, keeps backups and the undo journal, and tells the user which branch to repair before running stack sync again.

Do not edit .git/stack/state.json by hand. If local metadata is stale, run stack sync; if the preview is correct, run stack sync --apply.

Merge The Stack Root

stack merge
stack merge --apply
stack merge --auto
stack merge --auto --through stack-c

Prefer omitting the branch. stack merge infers the root from the current stack branch. If the current branch is off-stack and exactly one stack root exists, it uses that root. If multiple roots exist, it asks for stack merge <branch>.

Use bare stack merge as a dry-run. Add --apply only when the plan is correct. Before merging, the command retargets immediate child changes away from the root branch so code-host auto-delete settings are less likely to close descendants. Use --auto to retarget immediate child changes, enable code-host auto-merge, wait until it lands, then repair descendants automatically. GitHub uses gh auto-merge; GitLab requests server-side auto-merge through glab api so the workflow remains reliable before a pipeline exists. Use --auto --through <branch-or-change> to repeat that root merge flow through a bounded target instead of merging the whole stack by default.

--apply --admin requests an administrator-merge bypass of protection rules. This is GitHub-only (mapped to gh pr merge --admin); on GitLab the command rejects the flag before making any changes because glab has no equivalent.

Mutating merge workflows stream progress while they run. Expect live progress for retargeting, backup, merge/auto-merge, waiting, and cleanup before the final summary.

Understand Or Undo The Last Mutation

stack history
stack undo
stack undo --apply

Use history to inspect the saved undo journal. Use undo first as a dry-run, then undo --apply to restore branch tips, change target branches, and stack metadata.

Change Description Stack Blocks

stack sync --apply and stack merge --apply/--auto refresh a deterministic stack block in open change descriptions:

<!-- stack:links:start -->

### [Stack](https://github.com/kitlangton/stack)

1. #101
2. #102
3. **#103** 👈 current
<!-- stack:links:end -->

Earlier entries are landed history preserved from the previous block. The current change is bold and marked with 👈 current. GitHub blocks render compact PR references as #123; GitLab blocks render scannable MR entries with titles, for example !123 - Add parser. Branch paths are intentionally omitted from stack blocks.

Safety Rules

• Bare stack sync never mutates branches, changes, or stack metadata.
• stack merge is dry-run by default.
• Mutating commands need --apply, except stack merge --auto waits for the code host and repairs descendants after the root lands.
• Never mutate trunk branches such as dev, main, or master.
• Before rebasing a branch, the tool creates a local backup branch.
• If output is unclear, inspect with stack status, stack history, or command help before applying.

Do Not Use

Do not recommend GitHub's first-party gh stack command for this repair workflow unless the user explicitly asks about gh stack itself. This skill is for the local stack CLI.