Re: [PATCH 3/6] sparse-checkout: enable `set` to initialize sparse-checkout mode

> On Sat, Dec 4, 2021 at 1:40 PM Victoria Dye <vdye@github.com> wrote:
>>
>> Elijah Newren via GitGitGadget wrote:
>>> From: Elijah Newren <newren@gmail.com>
>>>
>>> The previously suggested workflow:
>>>    git sparse-checkout init ...
>>>    git sparse-checkout set ...
>>>
>>> Suffered from three problems:
>>>    1) It would delete nearly all files in the first step, then
>>>       restore them in the second.  That was poor performance and
>>>       forced unnecessary rebuilds.
>>>    2) The two-step process resulted in two progress bars, which
>>>       was suboptimal from a UI point of view for wrappers that
>>>       invoked both of these commands but only exposed a single
>>>       command to their end users.
>>>    3) With cone mode, the first step would delete nearly all
>>>       ignored files everywhere, because everything was considered
>>>       to be outside of the specified sparsity paths.  (The user was
>>>       not allowed to specify any sparsity paths in the `init` step.)
>>>
>>> Avoid these problems by teaching `set` to understand the extra
>>> parameters that `init` takes and performing any necessary initialization
>>> if not already in a sparse checkout.
>>>
>>
>> I really like this change! It always seemed weird that `set` would
>> implicitly `init`, but without any of the options in `init`.
>>
>>> Signed-off-by: Elijah Newren <newren@gmail.com>
>>> ---
>>>   builtin/sparse-checkout.c | 52 ++++++++++++++++++++++++++++++++++++++-
>>>   1 file changed, 51 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/builtin/sparse-checkout.c b/builtin/sparse-checkout.c
>>> index e252b82136e..cf6a6c6c3a7 100644
>>> --- a/builtin/sparse-checkout.c
>>> +++ b/builtin/sparse-checkout.c
>>> @@ -682,17 +682,26 @@ static int sparse_checkout_add(int argc, const char **argv, const char *prefix)
>>>   }
>>>
>>>   static char const * const builtin_sparse_checkout_set_usage[] = {
>>> -     N_("git sparse-checkout set (--stdin | <patterns>)"),
>>> +     N_("git sparse-checkout set [--cone] [--[no-]sparse-index] (--stdin | <patterns>)"),
>>
>> Since `cone` is an `OPT_BOOL`, shouldn't it appear in the usage string as
>> `--[no-]cone`? Without a `--no-cone` option, it's not clear how a user would
>> disable cone mode (since `set` preserves the existing cone mode setting if
>> `--cone` isn't given).
> 
> Yeah, fair point.  When copying from init I probably should have double checked.
> 
> Also, it makes me wonder if we should just make cone mode the default...
> 

>>>        NULL
>>>   };
>>>
>>>   static struct sparse_checkout_set_opts {
>>> +     int cone_mode;
>>> +     int sparse_index;
>>>        int use_stdin;
>>>   } set_opts;
>>>
>>>   static int sparse_checkout_set(int argc, const char **argv, const char *prefix)
>>>   {
>>> +     int mode, record_mode;
>>> +     const char *default_patterns[] = {"/*", "!/*/"};
>>> +
>>>        static struct option builtin_sparse_checkout_set_options[] = {
>>> +             OPT_BOOL(0, "cone", &set_opts.cone_mode,
>>> +                      N_("initialize the sparse-checkout in cone mode")),
>>> +             OPT_BOOL(0, "sparse-index", &set_opts.sparse_index,
>>> +                      N_("toggle the use of a sparse index")),
>>>                OPT_BOOL(0, "stdin", &set_opts.use_stdin,
>>>                         N_("read patterns from standard in")),
>>
>> I know this isn't part of this patch, but is `stdin` really a bool (i.e.
>> someone might specify `--no-stdin`)? If not, I think `OPT_SET_INT` might be
>> more appropriate.
> 
> Good point.  OPT_SET_INT() wouldn't fix it, though; you need to use
> OPT_BOOL_F or OPT_SET_INT_F and pass PARSE_OPT_NONEG as a flag.  I can
> include that.
> 
>>>                OPT_END(),
>>> @@ -700,11 +709,52 @@ static int sparse_checkout_set(int argc, const char **argv, const char *prefix)
>>>
>>>        repo_read_index(the_repository);
>>>
>>> +     set_opts.cone_mode = -1;
>>> +     set_opts.sparse_index = -1;
>>> +
>>>        argc = parse_options(argc, argv, prefix,
>>>                             builtin_sparse_checkout_set_options,
>>>                             builtin_sparse_checkout_set_usage,
>>>                             PARSE_OPT_KEEP_UNKNOWN);
>>>
>>> +     /* Determine if we need to record the mode; ensure sparse checkout on */
>>> +     record_mode = (set_opts.cone_mode != -1) || !core_apply_sparse_checkout;
>>> +     core_apply_sparse_checkout = 1;
>>> +
>>> +     /* If not specified, use previous definition of cone mode */
>>> +     if (set_opts.cone_mode == -1 && core_apply_sparse_checkout)
>>
>> I *think* this is supposed go before the `core_apply_sparse_checkout = 1;`
>> above it (if the intention is to only use the pre-existing cone mode setting
>> when already in a sparse checkout). If not, the `core_apply_sparse_checkout`
>> part of the condition is redundant and can be removed entirely.
> 
> Eek.  I had it there originally, then moved it later while doing
> various changes.  This definitely should be later; thanks for
> catching.
> 
>>> +             set_opts.cone_mode = core_sparse_checkout_cone;
>>> +
>>> +     /* Set cone/non-cone mode appropriately */
>>> +     if (set_opts.cone_mode == 1) {
>>> +             mode = MODE_CONE_PATTERNS;
>>> +             core_sparse_checkout_cone = 1;
>>> +     } else {
>>> +             mode = MODE_ALL_PATTERNS;
>>> +     }
>>> +     if (record_mode && set_config(mode))
>>> +             return 1;
>>> +
>>> +     /* Set sparse-index/non-sparse-index mode if specified */
>>> +     if (set_opts.sparse_index >= 0) {
>>> +             if (set_sparse_index_config(the_repository, set_opts.sparse_index) < 0)
>>> +                     die(_("failed to modify sparse-index config"));
>>> +
>>> +             /* force an index rewrite */
>>> +             repo_read_index(the_repository);
>>> +             the_repository->index->updated_workdir = 1;
>>> +     }
>>> +
>>> +     /*
>>> +      * Cone mode automatically specifies the toplevel directory.  For
>>> +      * non-cone mode, if nothing is specified, manually select just the
>>> +      * top-level directory (much as 'init' would do).
>>> +      */
>>> +     if (!core_sparse_checkout_cone && argc == 0) {
>>> +             argv = default_patterns;
>>> +             argc = 2;
>>> +     }
>>> +
>>>        return modify_pattern_list(argc, argv, set_opts.use_stdin, REPLACE);
>>>   }