Re: [PATCH] advice: warn when sparse index expands

[Derrick Stolee <stolee@gmail.com>]

On 7/5/24 4:29 PM, Elijah Newren wrote:
> On Wed, Jul 3, 2024 at 8:14 AM Derrick Stolee via GitGitGadget
> <gitgitgadget@gmail.com> wrote:
>>
>> From: Derrick Stolee <stolee@gmail.com>
>>
>> Typically, forcing a sparse index to expand to a full index means that
>> Git could not determine the status of a file outside of the
>> sparse-checkout and needed to expand sparse trees into the full list of
>> sparse blobs. This operation can be very slow when the sparse-checkout
>> is much smaller than the full tree at HEAD.
> 
> Yep, I'm with you here.
> 
>> When users are in this state, it is common that 'git status' will report
>> the problem.
> 
> I struggled to understand this sentence in combination with your later
> statements, though that may only be because I had some difficulty with
> later parts of the commit message.  Perhaps addressing the later parts
> will make this sentence fine as-is, but it's possible this sentence
> could do with a bit more detail.

I think also the issue with this sentence is that its thought isn't
complete until also reading the next one. These can be combined to
get to the point faster.

>> Usually there is a modified or untracked file outside of
>> the sparse-checkout mentioned by the 'git status' output. There are a
>> number of reasons why this is insufficient:
> 
> Fair enough; let's focus on why the output of git status is insufficient...
> 
>>   1. Users may not have a full understanding of which files are inside or
>>      outside of their sparse-checkout. This is more common in monorepos
>>      that manage the sparse-checkout using custom tools that map build
>>      dependencies into sparse-checkout definitions.
> 
> Having sparse-checkout patterns managed by custom tools is a really
> good point, but doesn't this statement of yours about needing to know
> particular files or directories suggest that...
>
>> +static int give_advice_on_expansion = 1;
>> +#define ADVICE_MSG \
>> +       "The sparse index is expanding to a full index, a slow operation.\n" \
>> +       "This likely means that you have files in your working directory\n"  \
>> +       "that are outside of your sparse-checkout patterns. Remove them\n"   \
>> +       "to recover performance expectations, such as with 'git clean'."
> 
> ...this is an insufficient solution?
> 
> I was a bit surprised you'd list your first reason for git status
> being insufficient, that users need to know which files/directories
> are the problem and then provide a solution that doesn't attempt to
> identify any files or directories.
> 
>>   2. In some cases, an empty directory could exist outside the
>>      sparse-checkout and these empty directories are not reported by 'git
>>      status' and friends.
> 
> This is a really good point too...but given this point, shouldn't your
> added advice message also mention "directories" instead of just
> mentioning "files" so that users are aware they need to look for those
> too?
> 
>>   3. If the user has '.gitignore' or 'exclude' files, then 'git status'
>>      will squelch the warnings and not demonstrate any problems.
> 
> Your solution does help the user to know that there is a problem (even
> if they don't know which files -- or directories -- are the problem),
> so this patch is making things better.

Thanks for pushing for a more helpful message. I'm currently thinking
that the core issue is that the working directory has contents (files
or directories) that disagree with the sparse-checkout definition. I
will update the language in v2 to point the user in the direction of
comparing the two.

Thanks,
-Stolee