Revisiting large binary files issue.

Hi,

Some of this stuff has been discussed before but I thought I'd bring it up again.

I am using git in a way for which, admittedly, it was not intended. I have repositories in which I'm storing some source code mixed with some large binary files (from 20MB up to 1GB in the worst case). The large files easily dominate the space in the repository and the time that it takes to perform network operations between repositories.

Just to refresh your memory a sample of these files led to work that Nicolas did to improve the performance of packing large binary files. Thank you Nicolas, I think your work improved the speed of git in the face of largish files.

Attempting to delta compress these blobs is a frivolous effort. The nature of the blobs is such that if given two blobs: 'A', and the next revision, 'B' it is just as good --- from a pack-size standpoint --- to compress the entire contents of 'B' than try to find a delta from A -> B. It is also much faster than trying to find deltas. In git, I can accomplish this by setting the pack window (I think this is right) to 0.

When I set the window to 0 I one more issue. Even though the blobs are already compressed on disk I still seem to pay the penalty of inflating them into memory and then deflating them into the pack. When the window size is 0 this is just wasted cycles. With large binary files these wasted cycles slow down the push/fetch operation considerably. Couldn't the compressed blobs be copied into the pack without first deflating them in this 0 window case?

My 'porcelain' on top of git works around these issues by first rsyncing the object directories and then running the git push/fetch command afterward. The push/fetch command sees that the remote is up-to-date with all the necessary objects and skips packing. This works and is fast (much faster than even packing with window of 0 because of the time to inflate/deflate the objects) but I'd like to remove this work-around in the long-term.

Ideally, there are two things that I would like available with git to be able to remove my work-around.

First, I would like to be able to set the packing window to 0 for all of the git commands. It would be nice if I could set this in a per-repository config file so that any push/fetch operation would honor this window. Is there currently a way to do this?

Second, I would like to not pay the penalty to inflate and then deflate the objects into the pack when I use a window of 0. How hard would this be? I am a capable programmer and wouldn't mind getting my hands dirty in the code to implement this if someone could point me in the right direction.

Thanks for your time, Carl Baldwin