Github release downloader

ghr

#!/bin/bash

set -euo pipefail

api_base='https://api.github.com'

usage() {
    cat <<'EOF'
Usage:
  ghr search QUERY...
  ghr releases OWNER/REPO
  ghr assets OWNER/REPO [TAG]
  ghr download OWNER/REPO TAG ASSET

Examples:
  ghr search powerpc browser
  ghr releases dillo-browser/dillo
  ghr assets owner/repo
  ghr assets owner/repo v1.2.3
  ghr download owner/repo v1.2.3 foo-powerpc.tar.gz
  ghr download owner/repo latest foo-powerpc.tar.gz
EOF
}

api_get() {
    curl -fsSL \
        -H 'Accept: application/vnd.github+json' \
        "$@"
}

release_url() {
    local repo=$1
    local tag=$2

    if [[ $tag == latest ]]; then
        printf '%s/repos/%s/releases/latest\n' "$api_base" "$repo"
    else
        printf '%s/repos/%s/releases/tags/%s\n' "$api_base" "$repo" "$tag"
    fi
}

cmd_search() {
    (($# > 0)) || {
        echo 'usage: ghr search QUERY...' >&2
        exit 2
    }

    curl -fsSLG \
        -H 'Accept: application/vnd.github+json' \
        --data-urlencode "q=$*" \
        --data-urlencode 'per_page=30' \
        "$api_base/search/repositories" |
        jq -r '.items[].full_name'
}

cmd_releases() {
    (($# == 1)) || {
        echo 'usage: ghr releases OWNER/REPO' >&2
        exit 2
    }

    api_get "$api_base/repos/$1/releases?per_page=100" |
        jq -r '.[] | [.tag_name, .name] | @tsv'
}

cmd_assets() {
    (($# >= 1 && $# <= 2)) || {
        echo 'usage: ghr assets OWNER/REPO [TAG]' >&2
        exit 2
    }

    local repo=$1
    local tag=${2:-latest}

    api_get "$(release_url "$repo" "$tag")" |
        jq -r '.assets[] |
            [.name, .size, .browser_download_url] |
            @tsv'
}

cmd_download() {
    (($# == 3)) || {
        echo 'usage: ghr download OWNER/REPO TAG ASSET' >&2
        exit 2
    }

    local repo=$1
    local tag=$2
    local asset=$3
    local url

    url=$(
        api_get "$(release_url "$repo" "$tag")" |
            jq -r --arg asset "$asset" '
                .assets[] |
                select(.name == $asset) |
                .browser_download_url
            '
    )

    if [[ -z $url ]]; then
        echo "ghr: asset not found: $asset" >&2
        exit 1
    fi

    curl -fL -O "$url"
}

main() {
    (($# > 0)) || {
        usage >&2
        exit 2
    }

    local command=$1
    shift

    case $command in
        search)
            cmd_search "$@"
            ;;
        releases)
            cmd_releases "$@"
            ;;
        assets)
            cmd_assets "$@"
            ;;
        download)
            cmd_download "$@"
            ;;
        -h|--help|help)
            usage
            ;;
        *)
            echo "ghr: unknown command: $command" >&2
            usage >&2
            exit 2
            ;;
    esac
}

main "$@"