create-prs-for-stack.sh

#!/usr/bin/env bash
# Given a commit sha (defaults to current commit), creates PRs for every
# branch on the stack of the given commit.  Each PR is created with its base
# as the nearest ancestor of the given branch that is also a branch.
set -euo pipefail

commit="${1:-.}"
base="$(git config branchless.core.mainBranch)"
remote="origin"

git-branchless submit --create "stack(\"$commit\")"

# FIXME: Remove `| tac` once
# https://github.com/arxanas/git-branchless/issues/554 is fixed
branches="$(git-branchless query -b "stack(\"$commit\")" | tac)"

while read -r branch <&3; do
    existing_pr="$(gh pr view "$branch" --json url -t "{{.url}}" || echo -n "")"

    if [ -n "$existing_pr" ]; then
        echo "PR $existing_pr already exists for branch $branch"
        continue
    fi

    ancestor_query="ancestors(parents(\"$branch\")) & branches() & draft()"
    parent_branch=$(git-branchless query -b "$ancestor_query - ancestors(parents($ancestor_query))")
    if [ -z "$parent_branch" ]; then
        parent_branch="$base"
    else
        if [[ $parent_branch =~ $'\n' ]]; then
            echo "ERROR: Branch $branch has more than one parent branch: $parent_branch"
            exit 1
        fi

        gh pr view "$parent_branch" --json url -t "Depends on {{.url}}" | pbcopy
        echo "Copied dependency message to clipboard for use in PR body"
    fi

    gh pr create \
        --draft \
        --base "$parent_branch" \
        --head "$branch"
done 3<<<"$branches"