mn

#!/bin/sh

# Move (`mv`) a file and then link (`ln`) to the new location from the old one.  Based on
# Gilles' answer [here][1].
#
# [1]: https://unix.stackexchange.com/a/228166 "Move a file and replace it by a symlink"

# TODO: think more about the case where "$original" is a directory (maybe ending with
# slash); there may be problems (see <https://unix.stackexchange.com/q/253524>).

# See <https://mywiki.wooledge.org/BashFAQ/112>.
set -o nounset

[ "$#" -ne 2 ] && { echo "$0: wrong number of parameters" >&2; exit 1; }

original="$1" target="$2"
if [ -d "$target" ]; then
   # When $2 is a directory, make sure `ln` will create a link to the moved file's new
   # location inside that directory, not to the directory itself.
   target="${target%/}/${original##*/}"
fi
mv -- "$original" "$target" || exit
case "${original%/}" in
   */*) # If the link may be created outside of the current directory...
      case "$target" in
         /*)
            : ;;
         *) # ...and the target path is not absolute, rewrite it to be absolute.
            target="$(cd -- "$(dirname -- "$target")" && pwd)/${target##*/}"
      esac
   # If the link will be in the current directory and "$target" is a relative path, that
   # relative path can be used as the link target directly since it is relative to the
   # link's location.
esac

# TODO: move the file back if `ln` fails?
ln -sT -- "$target" "${original%/}"