On 12/1/2021 12:16 PM, Elijah Newren wrote: > Hi, > > I've got a proposal for changing the sparse-checkout command slightly; > but it probably doesn't make sense without the context of the bugs > (old and new) we are facing. Consider this an RFC, with the final > bullet point particularly in need of comment and ideas. > > == Background == > > sparse-checkouts in cone mode are documented as being obtained either > by using the `--sparse` flag to `git clone`, ... The `--sparse` flag doesn't initialize cone mode, unfortunately. > git sparse-checkout init --cone [--sparse-index] > git sparse-checkout set ... > > The first step has traditionally deleted all the tracked files from > the working tree, except in the toplevel directory, and the second > restores all the tracked files that are wanted. > > (Usage context:) > My understanding is Microsoft never uses this sequence, instead using > the --sparse flag to `git clone`. In contrast, at Palantir the > --sparse flag to clone is rarely used. We use the sparse-checkout builtin. From the Scalar patch series, you can see that we don't call "git clone" at all, but instead "scalar clone" does a lot with "git init" and works from there by setting config and fetching at the correct time. > == The (New) Bug == > > Starting with Git 2.34, each step will delete all ignored files > outside the sparsity paths specified to the individual command in > question. We are totally onboard with deleting ignored files outside > the sparsity paths the user wants, but the first command is required > according to the documentation and does not allow specifying any > sparsity paths. Since it does not allow specifying any sparsity > paths, it treats *everything* as outside and essentially deletes all > ignored files everywhere. That's not workable for us. We want a > single command for changing to a sparse-checkout. Ah, since 'git sparse-checkout set' would work differently if not in cone mode, I see the problem. It's a little too much to manually set core.sparseCheckoutCone=true before running the 'set' command, probably. > == The Current Workaround == > > Luckily, having these two commands separate isn't enforced, and the > first command is basically roughly equivalent to setting a few config > variables and then running `sparse-checkout set` with an empty set of > paths. So, currently, we can just do the config setting part of init > manually, and then skip the rest of init, and then call our desired > `set` command: > git config extensions.worktreeConfig true > git config --worktree core.sparseCheckout true > git config --worktree core.sparseCheckoutCone true > git sparse-checkout set ... Which you have already worked out. > Since we're using a wrapper anyway (for computing dependencies and > determining the list of directories to include), it was relatively > easy for us to add this workaround. > > However, it is not clear that our current workaround will continue > functioning with future versions of git, particularly if > `sparse-checkout init` gains more options. In fact, it already > doesn't handle --sparse-index. Right. It's _yet another_ config option to tweak. > == Long term proposal == > > Make `set` do both the work of `init` and `set`. > > This means: > * `set` gains the ability to parse both --cone and --sparse-index > (in addition to --stdin, etc.) > * If the sparse-index is not initialized, `set` does the > initialization work of `init`. > * Modify the `init` documentation to mark it as deprecated, > mentioning the 2-3 bugs above as reasons why. > * We could effectively just turn `git sparse-checkout init ...` into > an alias for `git sparse-checkout set ...`, since init's parameters > would be a subset of those that `set` accepts. However, the latter > might interact badly with allowing a user to toggle sparse-index on > and off in the middle of a sparse-checkout...so maybe we need > something more? Alternatively, we could leave `init` as-is and just > consider it set in concrete, possibly risking it becoming > non-functional in a future upgrade. Hmm... I think this is a good plan. Making 'init' the same as 'set' with no paths makes sense to me. We would want to be careful now that "--option" could be interpreted as a path to recommend using git sparse-checkout set <options> -- <path1> ... <pathN> While you are here, I would be interested in making 'git clone --sparse' default to cone mode. Or, should it be 'git clone --sparse=cone' or something? Not making it default to cone mode is a big regret of mine. Thanks, -Stolee
