bug#9742: touch option for existence?

[Morty]

[This is more of a feature request than a bug request.  But I don't
see where I can make feature requests.]

It would be nice if touch had an option to only "touch" if the file
doesn't already exist.  Sort of like -c, but the other way around.
This is useful because often, the reason one is using "touch" in a
script is because one wants to make sure that a file exists before
doing an operation that expects the file to already exist.  But if the
file already exists, then touch has a side effect of changing the
mtime or the atime.  [On many systems, one can work on a file without
changing the atime thanks to mount options such as noatime or
relatime.]

It's easy enough to wrap touch in an if:

  if [ ! -e $file ]; then touch $file; fi

But it would be nicer if this common case were built in.  I would
suggest -e, for exists.  Thanks!

- Morty