git pack-objects input list

Hi,

While playing around with git-pack-objects, it seemed to me that the input it can take is not a simple list of object SHA1s. Unfortunately, the man page is not very verbose about that. While I'd happily send a patch for that, I'd prefer to actually know what kind of input it can take, and what it uses it for.

AFAICT, it can take the output of git-rev-list --all --objects (so, SHA1s followed by file names for blobs), which seems to be the same as what git-pack-objects --revs does internally, but it seems to have a string impact on how deltas are calculated (not giving file names makes it create a smaller pack in some cases, a bigger one in other cases).

Could someone knowing the delta calculation internals enlighten me ?

Thanks

Mike