Run dockerized mermaid more conveniently

mermaid

#! /bin/sh
#
# shellcheck disable=SC2006
#
IFILE="$1"

case "${IFILE}" in
   --help|help|-h|"")
      cat <<EOF >&2
Usage:
   mermaid <in-file> [out-filename] [options]

   The out-filename specifies the output format with its file extension. The
   default is '.png'. '.pdf' and '.svg' are also available, but '.svg' is
   apparently broken ATM. In-file can be located anywhere, but the output file
   will be placed into the same directory as in-file.

   See: https://github.com/mermaid-js/mermaid-cli for more info.

EOF

      docker run -u "`id -u`" -it minlag/mermaid-cli -h 2>&1 \
      | egrep -v '^  -[io]' \
      | tail +3 >&2

      exit 1
   ;;
esac

OFILENAME="$2"

IDIR="`dirname -- "${IFILE}" `"
case "${IDIR}" in
   /*)
   ;;

   .)
      IDIR="${PWD}"
   ;;

   *)
      IDIR="${PWD}/${IDIR}"
   ;;
esac

IFILENAME="`basename -- "${IFILE}" `"
if [ -z "${OFILENAME}" ]
then
   OFILENAME="${IFILENAME%.*}.png"
fi


docker run -u "`id -u`" \
           -it \
           -v "${IDIR}":/data \
           minlag/mermaid-cli \
               "$@" \
               -i "/data/${IFILENAME}" \
               -o "/data/${OFILENAME}"