ci: improve installer script

1. remove shasum and cosign
2. improve output and help

install.sh

@@ -0,0 +1,141 @@
+#!/bin/sh
+# shellcheck shell=dash
+
+set -e
+
+info() {
+  local _green='\033[0;32m'
+  local _no_color='\033[0m'
+
+  echo "  ${_green} INFO${_no_color} $1"
+}
+
+error() {
+  local _red='\033[0;31m'
+  local _no_color='\033[0m'
+
+  echo
+  echo "   ${_red}ERROR${_no_color} $1"
+
+  echo
+  echo "   If you need help, please start a discussion on Github:"
+  echo "   https://github.com/build-trust/ockam/discussions/new"
+  echo
+
+  exit 1
+}
+
+required() {
+  if ! command -v "$1" > /dev/null 2>&1; then
+    error "need '$1' (command not found)"
+  fi
+}
+
+detect_binary_file_name() {
+  info "Detecting Operating System and Architecture ..."
+
+  local _os_type _cpu_type _file_name
+  _os_type="$(uname -s)"
+  _cpu_type="$(uname -m)"
+
+  case "$_os_type" in
+    Darwin)
+      if [ "$_cpu_type" = i386 ]; then
+        # Darwin `uname -m` lies
+        if sysctl hw.optional.x86_64 | grep -q ': 1'; then
+          _cpu_type=x86_64
+        fi
+      fi
+
+      case "$_cpu_type" in
+        x86_64) _file_name="ockam.x86_64-apple-darwin";;
+        arm64) _file_name="ockam.aarch64-apple-darwin";;
+        *) error "Unsupported CPU type: ${_cpu_type} on MacOS"
+      esac
+    ;;
+    Linux)
+      case "$_cpu_type" in
+        x86_64 | aarch64) _file_name="ockam.$_cpu_type-unknown-linux-gnu";;
+        armv7l) _file_name="ockam.$_cpu_type-unknown-linux-gnueabihf";;
+        *) error "Unsupported CPU type: ${_cpu_type} on Linux";
+      esac
+    ;;
+    *) error "Unsupported operating system type: ${_os_type}"
+  esac
+
+  info "Detected Operating System Type: ${_os_type}"
+  info "Detected CPU Type: ${_cpu_type}"
+  info "Picked Released File Name: ${_file_name}"
+
+  return_value="$_file_name"
+}
+
+download() {
+  required curl
+  required grep
+  required awk
+  required sed
+
+  local _version _url
+  local _download_base_url="https://github.com/build-trust/ockam/releases/download"
+  local _api='https://api.github.com/repos/build-trust/ockam/releases'
+  local _binary_file_name="$1"
+
+  if [ "$2" ]; then
+    _version="$2"
+    _url="$_download_base_url/ockam_$_version/$_binary_file_name"
+  else
+    _url=$(curl --proto '=https' --tlsv1.2 --silent --fail --show-error "$_api")
+    _url=$(echo "$_url" | grep -i browser_download_url | grep "$_binary_file_name" | head -1 | awk '{print $NF}')
+    _url=$(echo "$_url" | sed -e 's/^"//' -e 's/"$//') # remove quotes
+    _version=$(echo "$_url" | awk -F'/' '{print $(NF-1)}' | cut -d '_' -f2) # change "ockam_v0.75.0" to "v0.75.0"
+  fi
+
+  info "Installing $_version"
+
+  info "Dowloading $_url"
+  curl --proto '=https' --tlsv1.2 --location --silent --fail --show-error --output "ockam" "$_url"
+  info "Downloaded ockam command in the current directory $(pwd)"
+
+  info "Granting permission to execute: chmod u+x ockam"
+  chmod u+x ockam
+}
+
+main() {
+  echo
+  local _yellow='\033[0;33m'
+  local _no_color='\033[0m'
+  local _version="$1"
+
+  detect_binary_file_name
+  local _binary_file_name="$return_value"
+
+  download "$_binary_file_name" "$_version"
+
+  echo
+  echo "   ${_yellow}GET STARTED:${_no_color}"
+  echo "       Ockam Command is ready to be executed in the current directory."
+  echo
+  echo "       You can execute it by running:"
+  echo "         ./ockam"
+  echo
+  echo "       If you wish to run it from anywhere on your machine ..."
+  echo
+  echo "       Please copy it to a directory that is in your \$PATH, for example:"
+  echo "         mv ockam /usr/local/bin"
+  echo
+  echo "       After that, you should be able to execute it anywhere by simply typing:"
+  echo "         ockam"
+  echo
+  echo "   ${_yellow}LEARN MORE:${_no_color}"
+  echo "       Learn more at https://docs.ockam.io/get-started#command"
+  echo
+  echo "   ${_yellow}FEEDBACK:${_no_color}"
+  echo "       If you have any questions or feedback, please start a discussion"
+  echo "       on Github https://github.com/build-trust/ockam/discussions/new"
+  echo
+
+  exit 0
+}
+
+main "$1"