Add Stacked PR Breadcrumbs

Generate a stacked PR breadcrumbs block to add at the beginning of a PR body.

Instructions

Use gh stack view --json to get the stack. The .branches array is ordered from bottom (closest to trunk) to top; each entry has a pr.number (omitted if the branch has no PR). Generate the breadcrumbs in this exact format:

> [!IMPORTANT]
> This is a stacked PR:
> - #<base_pr>
> - #<current_pr> :point_left:
> - #<child_pr>

The list lines can be generated with:

gh stack view --json | jq -r --argjson current <pr_number> '.branches[] | select(.pr != null) | "> - #\(.pr.number)\(if .pr.number == $current then " :point_left:" else "" end)"'

<prnumber> is the number of the PR being edited — --argjson current passes it to jq as $current, and the filter appends :pointleft: to the line whose .pr.number matches it. Get it with gh pr view --json number -q .number when on the PR's branch.

Use gh to add the generated breadcrumbs block to the PR. If the PR already has a breadcrumbs block, replace it with the new one. Use a temp file for the PR body to ensure correct format.

Rules

1. List PRs as a flat list in stack order (bottom to top, as given by .branches) — there is only one chain, so no nesting
2. The current PR (the one being created/edited) should have :point_left: at the end
3. Always start with the > [!IMPORTANT] callout
4. Always include the header line > This is a stacked PR:
5. Each PR number should be prefixed with #
6. All lines must start with > to maintain the blockquote format

Example with 3 PRs in stack

If gh stack view --json returns branches with PRs #948, #950, and current PR #951

Output:

> [!IMPORTANT]
> This is a stacked PR:
> - #948
> - #950
> - #951 :point_left:

Example with 2 PRs in stack

If gh stack view --json returns branches with PRs #948, and current PR #950

Output:

> [!IMPORTANT]
> This is a stacked PR:
> - #948
> - #950 :point_left: