Diff between two crate versions

crate-diff.sh

#!/usr/bin/env bash
set -e

CRATES_IO_REGISTRY="$HOME/.cargo/registry/src/github.com-1ecc6299db9ec823"

display_usage() {
    echo "Usage: crate-diff.sh CRATE_NAME OLD_VERSION NEW_VERSION"
}

if [ $# -ne 3 ]
then
    display_usage
    exit 1
fi

if [[ ( $# == "--help" ) || ( $# == "-h" ) ]]
then
    display_usage
    exit 0
fi

TMPDIR="$(mktemp -d)"
if [[ ! "$TMPDIR" || ! -d "$TMPDIR" ]]
then
    echo "Couldn't create temporary directory"
    exit 1
fi
function cleanup {
    rm -rf "$TMPDIR"
}
trap cleanup EXIT

download_crate_version(){
    cd "$TMPDIR"
    mkdir -p src
    touch src/lib.rs
    cat <<EOF >Cargo.toml
[package]
name = "cargo-fetch-stub"
version = "0.0.1"

[dependencies]
EOF
    echo "$1 = \"$2\"" >>Cargo.toml
    cargo fetch
    cd - >/dev/null
}

download_if_needed(){
    if [[ ! -d "$CRATES_IO_REGISTRY/$1-$2/" ]]
    then
        download_crate_version "$1" "$2"
    fi
}

download_if_needed "$1" "$2"
download_if_needed "$1" "$3"
diff -r -u --color=auto "$CRATES_IO_REGISTRY/$1-$2/" "$CRATES_IO_REGISTRY/$1-$3/"