git-gone

#!/bin/bash

set -euo pipefail

# Delete local branches whose head commit is the same as that of a PR that has
# been merged.

DRY_RUN=0
DEBUG=0

function usage() {
    echo "usage: git gone [-n|--dry-run|--dry_run] [--debug]" >&2
    exit 1
}

while (( "$#" )); do
    case "$1" in
        -n|--dry-run)
            DRY_RUN=1
            shift 1
            ;;
        --debug)
            DEBUG=1
            shift 1
            ;;
        *)
            echo "Unsupported argument $1" >&2
            usage
            ;;
    esac
done

if (( DEBUG == 1 )); then
    set -x
fi

function main() {
    readarray -t branches < <(git for-each-ref --format='%(refname:short)' refs/heads/)
    local -a gh_branch_filter=("${branches[@]/#/head:}")

    # We filter to only PRs with head branches matching our local branches,
    # except that the gh CLI uses the search endpoint here, which does a prefix
    # match for branch names
    # (https://docs.github.com/en/search-github/searching-on-github/searching-issues-and-pull-requests#search-by-branch-name),
    # so we have to then filter client side with jq (using the `--head` flag
    # only allows a single input, so that doesn't work either). Finally, we
    # group by the branch name, since multiple PRs could've used the same branch
    # name and break out the json arrays for each branch name into separate
    # entries in a bash array. 
    readarray -t json_prs_by_branch < <(\
        gh pr list \
        --limit 1000 \
        --state merged \
        --author "@me" \
        --search "${gh_branch_filter[*]}" \
        --json 'headRefOid' --json 'headRefName' --json 'number' --json 'url' \
        | jq -c '. | map(select([.headRefName] | inside($ARGS.positional))) | group_by(.headRefName)[]' \
            --args "${branches[@]}"
    )

    if (( ${#json_prs_by_branch[@]} == 0 )); then
        echo "Found no matching PRs for local branches"
    fi

    for json_branch_prs in "${json_prs_by_branch[@]}"; do
        branch="$(jq -r '.[0].headRefName' <<< "${json_branch_prs}")"
        local_head_commit="$(git rev-parse "${branch}")"
        merged=0

        readarray -t json_prs < <(jq -c 'sort_by(.number) | .[]' <<< "${json_branch_prs}")
        for json_pr in "${json_prs[@]}"; do
            pr_head_commit="$(jq -r '.headRefOid' <<< "${json_pr}")"
            pr_number="$(jq -r '.number' <<< "${json_pr}")"
            pr_url="$(jq -r '.url' <<< "${json_pr}")"

            if [[ "${pr_head_commit}" == "${local_head_commit}" ]]; then
                merged=1
                break
            fi
        done
        if (( merged==1 )); then
            # No newline so the git output is on the same line
            echo -n "Deleting branch '${branch}' for merged PR #${pr_number} (${pr_url}): "
            if (( DRY_RUN == 0 )); then
                git branch -D ${branch}
            else
                # Since we didn't do a newline above, we need to add one if we don't actually run the git command above
                echo ''
            fi
        else
            echo "Not deleting '${branch}'. No matching PRs have a matching head commit ${local_head_commit}. Found matching PRs:"
            for json_pr in "${json_prs[@]}"; do
                pr_head_commit="$(jq -r '.headRefOid' <<< "${json_pr}")"
                pr_number="$(jq -r '.number' <<< "${json_pr}")"
                pr_url="$(jq -r '.url' <<< "${json_pr}")"
                echo "    #${pr_number} (${pr_url}): ${pr_head_commit}"
            done
        fi
    done
}

main