Re: [PATCH 2/3] sparse-checkout: add 'clean' command

> "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:
> 
>> From: Derrick Stolee <stolee@gmail.com>
>>
>> When users change their sparse-checkout definitions to add new
>> directories and remove old ones, there may be a few reasons why
>> directories no longer in scope remain (ignored or excluded files still
>> exist, Windows handles are still open, etc.). When these files still
>> exist, the sparse index feature notices that a tracked, but sparse,
>> directory still exists on disk and thus the index expands. This causes a
>> performance hit _and_ the advice printed isn't very helpful. Using 'git
>> clean' isn't enough (generally '-dfx' may be needed) but also this may
>> not be sufficient.
>>
>> Add a new subcommand to 'git sparse-checkout' that removes these
>> tracked-but-sparse directories, including any excluded or ignored files
> 
> Are excluded files and ignored files form two separate sets, or are
> they one and the same?  Do files that users forgot to add (e.g. new
> source file that would not match any patterns listed in .gitignore)
> and object files left over from the previous compilation (most
> likely match *.o in .gitignore) treated the same way for the purpose
> of determining if the directory that is no longer in the cone can be
> removed?

>> underneath. This is the most extreme method for doing this, but it works
>> when the sparse-checkout is in cone mode and is expected to rescope
>> based on directories, not files.
>>
>> Be sure to add a --dry-run option so users can predict what will be
>> deleted. In general, output the directories that are being removed so
>> users can know what was removed.
> 
> Hmph.  It would be safer to show not just the directories but which
> excluded files are about to be lost, wouldn't it, especially when
> the user is trying to play safe and see what potential damage they
> are looking at?
> > Also even though ignored files are "ignored and expendable", nobody
> marks their temporary file as "ignored but precious" (yet), so "it
> is listed in .gitignore so we can safely remove it" may not be a
> safe assumption for us to be making (yet).  Shouldn't we at least be
> listing these ignored files in --dry-run output, next to those files
> that the user may have forgotten to add?

>> Note that untracked directories remain. Further, directories that
>> contain staged changes are not deleted. This is a detail that is partly
>> hidden by the implementation which relies on collapsing the index to a
>> sparse index in-memory and only deleting directories that are listed as
>> sparse in the index. If a staged change exists, then that entry is not
>> stored as a sparse tree entry and thus remains on-disk until committed
>> or reset.
> 
> Removing untracked directories is a job for "clean -d", so it makes
> sense for this new command not to touch them.  Not losing changes
> that have already been added is just a bad as losing new files that
> the user forgot to add, so it does make sense not to remove them.
> 
> I wonder if we need "-x" and/or "-X" options "clean" has (and
> perhaps "-d" that is a no-op, as the whole point of this subcommand
> is about removing directories from the working tree) to control its
> operation a bit finer-grained way.