Mutt inline patch handling
       Developers like to send diffs inline in emails. They do this, because
       it's fast and easy to read through them, comment on them and also to
       apply them. Many version control systems take over the email text into
       he patch description as well.
       Up to now, my workflow was manual. I had to save the email somewhere,
       then open a terminal, cd to the direcory the patch shall be applied in
       and call the patch utility with the path to the saved email as argument.
       No more.
       This mutt macro takes the current visible email and copies it to a
       temporary file (/tmp/mutt-patch.diff). Then it executes the
       shell script. All with one push on ctrl+s while looking at the email.
       The macro must be written in one line and ^S can be entered with the
       keyboard sequence ctrl+v ctrl+s:
           macro pager ^S "<shell-escape>rm -f /tmp/mutt-patch.diff<enter>
           echo 'Saved as /tmp/mutt-patch.diff'<enter><shell-escape>
           ~/.mutt/scripts/ /tmp/mutt-patch.diff<enter>"
       The script:
           printf '\n-------------------------------------------------------\n'
           cat "$1" | egrep ^Index\|^RCS\|--git
           printf '-------------------------------------------------------\n\n'
           printf "Path for patch [/usr/ports]? "
           read _path
           [ -z "$_path" ] && _path=/usr/ports
           doas patch -p0 -d $_path < "$1"
           cd $_path && ksh
       The script shows some relvant bits from the email patch that are handy 
       to determine on which path the patch shall be applied.
       Next it alles the user to enter a different path. I most use /usr/ports, 
       so this is the default. Then the patch is applied and a ksh shell is 
       opened for further work.
       Quitting the shell brings me back to mutt to work on the next email.
       This is quite friggin handy.
       # Changelog:
       # * 2021-01-09: Created