This is a complement to the pristine-tar(1) command. Normally you don't need to run it by hand, since
pristine-tar calls it as necessary to handle .tar.xz files.
pristine-xz gendelta takes the specified xz file, and generates a small binary delta file that can later
be used by pristine-xz genxz to recreate the original file.
pristine-xz genxz takes the specified delta file, and compresses the specified input file (which must be
identical to the contents of the original xz file). The resulting file will be identical to the original
gz file used to create the delta.
The approach used to regenerate the original xz file is to figure out how it was produced -- what
compression level was used, etc. Currently support is poor for xz files produced with unusual compression
options.
If the delta filename is "-", pristine-xz reads or writes it to stdio.