enable runtime substitution in outputformat options

[msmitherdc]

Mainly interested in changing exporting FILENAME at runtime, eg

OUTPUTFORMAT
  NAME "SHAPEZIP"
  DRIVER "OGR/ESRI Shapefile"
  FORMATOPTION "STORAGE=memory"
  FORMATOPTION "FORM=zip"
  FORMATOPTION "FILENAME=%filename%"
END

[dmorissette]

Steve, Frank, what do you think of this addition? Should we do it only for FORMATOPTION or should we allow it for all outputformat params?

[warmerdam]

I think it would also be very useful to offer this for the DRIVER line. While at it, perhaps also the rest of the options?

[aboudreault]

There is a patch in #3652 that looks ok, if there are only a few options. We would have to determine all the options that can be substituted. Otherwise, we'd need to think about another approach.

[aboudreault]

About my last comment, I had environment variables to modify existing options in mind, not substitute a variable in the mapfile. The patch mentionned is not appropriate (or incomplete) for this case.

[mko]

Replying to aboudreault:

There is a patch in #3652 that looks ok, if there are only a few options. We would have to determine all the options that can be substituted. Otherwise, we'd need to think about another approach.

In #3652 I plan to use url substitution syntax so one can do the same as url substitutions but with environment variables.