2008/11/14 Nagy Gabor <ngaba@bibl.u-szeged.hu>:
Idézet Xavier <shiningxc@gmail.com>:
On Fri, Nov 14, 2008 at 1:02 PM, Nagy Gabor <ngaba@bibl.u-szeged.hu> wrote:
I guess I spoke to soon. I was right concerning xdelta3 using gzip for handling gzipped files, however it doesn't use the -n flag. This gives us the same behaviour as xdelta1, with one minor difference: Method 1. stops working.
Wait. I don't understand something. If it doesn't use the -n flag, how can we produce an md5sum-identical patched file? (The mtime is unpredictable.) This poses an extra problem, or not? I just did an effective test on xdelta3-diffing .tar.gz files and I saw that the patched md5sum indeed differ from the original one :-( Maybe we should search for a gzip header manipulation tool...
One of the proposal was to use gzip -n, which should fix this problem.
xdelta1 used(?) "gzip -n" for _patched_ .tar.gz file, xdelta3 doesn't use "-n", so setting "-n" for the original .tar.gz file won't help any more. Probably xdelta3 also can be configured or patched to use "-n"... Or I may completely misunderstood something...
xdelta1 uses zlib, my proposal was taking the uncompressed output of xdelta1 and using gzip -n to compress it. xdelta3 uses gzip, but without -n. I can't find any options for external compression, but the easiest thing to do would be deactivating external compression in xdelta3 and apply it manually by piping the output through gzip -n.