On Mon, Aug 30, 2021 at 6:19 AM Derrick Stolee <stolee@xxxxxxxxx> wrote: > > On 8/27/2021 5:33 PM, Elijah Newren wrote: > > On Tue, Aug 24, 2021 at 2:51 PM Derrick Stolee via GitGitGadget > > <gitgitgadget@xxxxxxxxx> wrote: > >> > >> From: Derrick Stolee <dstolee@xxxxxxxxxxxxx> > >> > >> When updating the cache tree in convert_to_sparse(), the > >> WRITE_TREE_MISSING_OK flag indicates that trees might be computed that > >> do not already exist within the object database. > > > > Okay. > > > >> This happens in cases > >> such as 'git add' creating new trees that it wants to store in > >> anticipation of a following 'git commit'. > > > > This doesn't make any sense to me. Does 'git add' call > > convert_to_sparse()? I don't see why it would; wouldn't the calls to > > convert_to_sparse() come via sparse-checkout init/set commands? If > > I'm correct on that, and 'git add' wants to create new trees, then by > > the time convert_to_sparse() is called in some subsequent git > > operation, then convert_to_sparse would already have the trees it > > needs. > > If someone adds a change outside the sparse-checkout cone, then the > index is expanded in-memory, then is converted to sparse when the > index is written again. Ah, I missed that convert_to_sparse() is called from write_index(), and that we are dealing with a single operation that does a sparse->full (in memory)->sparse roundtrip. Thanks for clearing that up. > > I thought the reason you would need this is someone modified and > > staged a change to a file underneath a directory that will be > > sparsified away; at the time of convert_to_sparse(), a tree object may > > not have yet been written for the new tree with the newly modified > > file (because those tend to be written at commit time), but you'd need > > it at the time you sparsified. > > Yes. I think we are trying to say the same thing. While writing this, I was thinking in terms of the `git add` being done when the index was full (both in memory and on disk), and then a later `git sparse-checkout ...` command would invoke the convert_to_sparse(). I didn't fully catch the nuances here. Thanks for bringing me up to speed.
