Some golang tools for working with initrd files. An example script using the available tools is provided which should be capable of extracting any (gzipped) initrd and reconstructing it (most likely with some changes).
A Makefile is provided for easier building - simply type make to build both binaries.
Extract a gzipped data file (GZIP_FILE) to OUTFILE and put and trailing data in TRAILER for further processing.
Usage: gunzip-trailer GZIP_FILE OUTFILE TRAILER
Get the length of gzip data before any trailing data in FILENAME.
Usage: gzip-length FILENAME