The `cups-drv-rastertosag-gdi` CUPS printer driver
package provides a filter executable `rastertosag-gdi`
and two ppd files that reference the filter file.
The commit at hand uses `patchPpdFilesHook` to
replace calls to the filter executable with
absolute paths to increase package purity.
Some Ricoh printers use the proprietary sag-gdi format
and can't handle other, more common formats.
This commit brings a filter for cups
that generates the sag-gdi format.
The latest version 0.1 is dated 2011. So updates are unlikely.
The filter is written for Python 2.
To avoid new reverse dependencies on Python 2,
we employ a patch from Debian
that migrates the code to Python 3.
The README file just states "GPL" as license.
It is unclear whether that refers to the first version or
to the "current version" in the year of the copyright
(would be 3), and whether newer versions would be included.
The commit picks the nixpkgs `free` license
as this seems to be the most general license
covering all possible GPL combinations.
At least, `free` should permit Hydra to build the package.
The source tarball brings pdd files, but also a
drv file that can be used to generate those ppd files.
Since we prefer building from source,
we call cups' `ppdc` to build ppd files from the drv file.
Here is a documentation of the sag-gdi format:
https://www.undocprint.org/formats/page_description_languages/sagem-gdi
