A script to safely download and try the newest opam release

try-opam-2.sh

#!/bin/bash -ue

VERSION=2.0.0~beta4

MINORV=${VERSION##*[^0-9]}
BASEV=${VERSION%$MINORV}

CURRENT_VERSION=$(opam --version --safe)
if [ $? -ne 0 ]; then CURRENT_VERSION=none; fi
if [ -z "${OPAMROOT:-}" ]; then OPAMROOT=~/.opam; fi

NOBACKUP=0
FRESH=0

while [ $# -gt 0 ]; do
    case "$1" in
        --revert)
            if [ -e "$OPAMROOT.bak" ]; then
                rm -rf "$OPAMROOT"
                mv "$OPAMROOT.bak" "$OPAMROOT"
                echo "Opam reverted to the backup at $OPAMROOT.bak"
                exit 0
            else
                echo "No opam 1.2 backup found" >&2
                exit 1
            fi
            ;;
        --no-backup)
            NOBACKUP=1
            ;;
        --fresh)
            FRESH=1
            ;;
        --root)
            if [ $# -lt 2 ]; then
                echo "Option $1 requires an argument";
                exit 2
            fi
            shift
            OPAMROOT=$1
            ;;
        --help|-help|-h)
            echo "Usage: $0 [--revert] [--no-backup] [--help] [VERSION]"
            echo "  --revert     restore the backup and revert to the previous opam version"
            echo "  --no-backup  don't backup the opam root (it will be upgraded or destroyed)"
            echo "  --fresh      start with a fresh opam root instead of an existing one"
            echo "  VERSION      the new opam version to install. Defaults to $VERSION."
            echo "               It must be newer than the current version"
            exit 0
            ;;
        -*)
            echo "Invalid option $1. Try '--help'." >&2
            exit 2
            ;;
        *)
            VERSION=$1
    esac
    shift
done

recursive_backup() {
    if [ -e "$1" ]; then
        recursive_backup "$1.bak"
        mv "$1" "$1.bak"
    fi
}

case "$CURRENT_VERSION" in
    1.2.*)
        echo "# opam 1.2 detected. Your opam root will be backed up as '$OPAMROOT.bak'"
        USE_UPGRADE=1
        BINDIR=$OPAMROOT
    ;;
    $BASEV*)
        if ! [ "${CURRENT_VERSION#$BASEV}" -lt "$MINORV" ]; then
            echo "Newer or conflicting installed opam version found ($CURRENT_VERSION)"
            exit 1
        else
            USE_UPGRADE=1
            BINDIR=$OPAMROOT
        fi
    ;;
    2.0.0~*)
        USE_UPGRADE=1
        BINDIR=$OPAMROOT
    ;;
    1.0.*|1.1.*|none)
        if [ -d "$OPAMROOT" ]; then
            if [ "NOBACKUP" = "1" ]; then
                rm -rf "$OPAMROOT"
                echo "removed old opam root at '$OPAMROOT'"
            else
                recursive_backup "$OPAMROOT"
                echo "old opam root detected, backed up as '$OPAMROOT.bak'"
            fi
        fi
        echo "Please choose a directory where the binary should be installed (it should be in"
        echo "your PATH)"
        printf "Binary directory (default /usr/local/bin): "
        read BINDIR
        if [ "x" = "x$BINDIR" ]; then BINDIR=/usr/local/bin; fi
    ;;
    *)
        echo "Newer or conflicting installed opam version found ($CURRENT_VERSION)"
        exit 1
esac


ARCH=$(uname -m)
case "$ARCH" in
    x86|i?86) ARCH="i686";;
    x86_64|amd64) ARCH="x86_64";;
    ppc|powerpc|ppcle) ARCH="ppc";;
    aarch64_be|aarch64|armv8b|armv8l) ARCH="arm64";;
    armv5*|armv6*|earmv6*|armv7*|earmv7*) ARCH="armhf";;
    *) ARCH=$(awk '{print tolower($0)}' <<<"$ARCH")
esac

OS=$(uname -s)
case "$OS" in
    darwin|macos) OS=darwin;;
    *) OS=$(awk '{print tolower($0)}' <<<"$OS")
esac

OPAM_BIN="opam-${VERSION/\~/-}-${ARCH}-${OS}"
OPAM_BIN_URL="https://github.com/ocaml/opam/releases/download/${VERSION/\~/-}/${OPAM_BIN}"

TEMP_OPAM=$(mktemp /tmp/$OPAM_BIN.XXXXX)
trap "rm -f \"$TEMP_OPAM\"" EXIT
chmod a+x "$TEMP_OPAM"

download() {
    if command -v wget >/dev/null; then wget -q -O "$@"
    else curl -s -L -o "$@"
    fi
}

echo "# Downloading opam for your system ($OS/$ARCH)"
if ! download "$TEMP_OPAM" "$OPAM_BIN_URL"; then
    echo "Sorry, could not download a binary for your platform. Check"
    echo "https://github.com/ocaml/opam/releases/tag/${VERSION/\~/-}, or please use the"
    echo "source"
    exit 1
fi

if [ "$USE_UPGRADE" = "1" ]; then
    if [ "$FRESH" = "1" ]; then
        if [ "$NOBACKUP" = "0" ]; then
            recursive_backup "$OPAMROOT"
        else
            rm -rf "$OPAMROOT"
        fi
        mkdir -p "$OPAMROOT"
    elif ! [ "$NOBACKUP" = "1" ]; then
        echo "# Backing up $OPAMROOT (this may take a while)"
        FREE=$(df -k "$OPAMROOT" | awk 'NR>1 {print $4}')
        NEEDED=$(du -s "$OPAMROOT" | awk '{print $1}')
        if ! [ $NEEDED -lt $FREE ]; then
            echo "Error: not enough free space to backup. You can retry with --no-backup,"
            echo "--fresh, or remove '$OPAMROOT'"
            exit 1
        fi
        recursive_backup "$OPAMROOT.bak"
        cp -a "$OPAMROOT" "$OPAMROOT.bak"
    fi
    echo "$VERSION" > "$OPAMROOT/opam.version"
    mv "$TEMP_OPAM" "$OPAMROOT/opam"
    rm -f "$OPAMROOT/repo/state.cache"
    if [ "$FRESH" = "0" ]; then
        echo "# Converting the opam root format"
        opam update --yes >/dev/null
        echo "# Updating the repositories"
        opam update
        echo
        echo "# opam $VERSION installed"
    else
        echo "# Initialising opam"
        opam init
        echo
        echo "# opam $VERSION installed"
    fi
    echo
    echo "Note: system opam is still $CURRENT_VERSION, as reported by 'opam --version',"
    echo "      but $OPAMROOT is set to switch automatically"
    echo "      to the newer $VERSION"
else
    if [ -w "$BINDIR" ]; then
        mv "$TEMP_OPAM" "$BINDIR/opam"
    else
        echo "Root access is needed to write to $BINDIR:"
        echo "    sudo mv \"$TEMP_OPAM\" \"$BINDIR/opam\""
        sudo mv "$TEMP_OPAM" "$BINDIR/opam"
    fi
    if [ "$(opam --version)" != "$VERSION" ]; then
        FOUND_OPAM=$(command -v opam || echo $BINDIR/opam)
        if [ $FOUND_OPAM != $BINDIR/opam ]; then
            echo "WARNING: a different opam is present at $FOUND_OPAM. Remove it, rename it or"
            echo "fix your PATH to use the newer one"
        else
            echo "Newer opam reports an incorrect version, aborting. Please file a bug report to"
            echo "https://github.com/ocaml/opam/issues with the following information:"
            opam config report
        fi
    fi
    echo "Opam $VERSION installed. Run 'opam init' to get started"
fi