On Mon, 2020-02-10 at 10:02 -0500, Derrick Stolee wrote: > Git loads the multi-pack-index file, which includes a sorted list of > the packs it covers. It then scans the "pack" directory for pack-indexes > and checks if they are covered by the multi-pack-index. If not, then > Git will add them to the packed_git struct and use them as normal. > The hope is that this list of "uncovered" packs is small compared to > the data covered by the multi-pack-index. > > This allows Git to continue functioning after an action like "git fetch" > that adds a new pack but may not want to rewrite the multi-pack-index. Ah, ok. So then perhaps I'll just make bup write the multi-pack-index file as is. This is fine, there's no real need to have multiple, I just didn't want to have to make sure the file was always consistent. Or maybe just call git to do it, and only be able to read the resulting file :-) > Our background maintenance essentially runs these commands: > > 1. git multi-pack-index write > 2. git multi-pack-index expire > 3. git multi-pack-index repack > > Step 1 ensures all packs are pulled into the multi-pack-index. Step 2 > deletes any pack-files whose objects are contained in newer pack-files. > Step 3 creates a new pack-file containing all objects from a set of > small pack-files (using the --batch-size=X option). This process helps > incrementally reduce the size and number of packs. That may be helpful > for your backup took, too. I'll have to look at this in more detail later, and understand exactly what the steps do here. Evidently that modifies pack files, which I hadn't expected for a type of "index" command :-) > Perhaps after an incremental multi-pack-index is added, then Git could > (optionally) have a mode that only checks the multi-pack-index to > avoid scanning the packs directory. It would require inserting a > multi-pack-index write into the index-pack logic so Git. I guess you'd still want to read non-covered pack files just in case old git was used or something though. > I'm not sure if that mode would be helpful, since the pack directory > scan is typically done once per command and is relatively fast. Right. > > > That said: if someone wanted to contribute an incremental format, > > > then I would be happy to review it! > > > > I might still get motivated to do so :-) > > YOU CAN DO IT! (Did that help?) :-) Thanks, johannes
