feat: print usage

mygb.sh

@@ -15,4 +15,71 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
-echo "Hello World !"
+# Constant
+readonly USAGE='
+mygb.sh <command> [options]                                           \n
+                                                                      \n
+Command :                                                             \n
+init : create the configuration file                                  \n
+export : export from GitLab                                           \n
+import : import to GitLab                                             \n
+                                                                      \n
+Options :                                                             \n
+ -h                : print help                                       \n
+ -c path/to/conf   : read one config file                             \n
+ -p path/to/projet : export the projet                                \n
+ -g path/to/group  : export the group and is subgroups and projects   \n
+ -a                : export all my group and subgroup                 \n
+'
+
+# Vars
+config_file='.mygb_config'
+export_all=false
+
+_help() {
+  echo -e "${USAGE}"
+  exit 1
+}
+
+_load_config() {
+  if [[ -e ${config_file} ]]; then
+    # shellcheck disable=SC1090
+    source ${config_file}
+  else
+    _create_config
+  fi
+}
+
+_create_config() {
+  echo "There is no file!"
+
+  echo "What is the GitLab URL :"
+  read -r gitlab_url
+
+  echo "What is the GitLab API token :"
+  read -rs gitlab_api_token
+
+  echo "gitlab_url=\"${gitlab_url}\"" >${config_file}
+  echo "gitlab_api_token=\"${gitlab_api_token}\"" >>${config_file}
+
+  echo "The file ${config_file} was created with this content."
+  echo "Please add the line below on your .gitignore"
+  echo "${config_file}"
+}
+
+main() {
+  echo "My GitLab Backup"
+  while getopts c:p:g:ah flag; do
+    case "${flag}" in
+    c) config_file=${OPTARG} ;;
+    p) project=${OPTARG} ;;
+    g) groups=${OPTARG} ;;
+    a) export_all=true ;;
+    h | *) _help ;;
+    esac
+  done
+
+  _load_config
+}
+
+main "$@"