Re: [RFC PATCH 0/6][GSoC] iterate dirs before or after their contents

[Phillip Wood <phillip.wood123@gmail.com>]

Hi Plato

I think this would be a useful addition to git, thanks for working on 
it. I've left some comments on the individual patches. In general I 
think this series would benefit from trying to work with the existing 
code and change one aspect at a time in stages rather than rewriting 
large chunks all at once.

Best Wishes

Phillip

On 10/04/2022 12:18, Plato Kiorpelidis wrote:
> Hello. Some time ago I worked on converting opendir/readdir calls to use
> dir-iterator [1], however this cleanup required to iterate directory paths after
> their contents. Matheus pointed me out to a previous patch series[2] that
> attempted to implement such functionality in dir-iterator. From it, I mainly
> used Michael's feedback and feature requests and tried to include it in my work.
> 
> My fork: https://github.com/kioplato/git/tree/dir-iterator
> CI: https://github.com/kioplato/git/actions/runs/2141288008
> There are some memleaks, I'll track them down in v2.
> 
> I aim to implement more functionality in dir-iterator, my goal being to simplify
> the codebase by introducing an abstraction layer for iterating directories.
> I would like to eventually simplify read_directory_recursive(). I wanted to
> check in with you to make sure I'm heading in the right direction with what I've
> implemented.
>    * Are my tests overly exhaustive?
>    * As of now we can't thoroughly test dir-iterator on directories with complex
>    structure since readdir produce dirents with undefined order in a directory.
>    I thought about introducing a tool for generating permutations with stable
>    parts in test-lib. Is there a need to something like this for other tests?
>    Or maybe should I sort each level iterated by dir-iterator inside
>    test-dir-iterator before printing to stdout? In these patches I did enumerate
>    the path permutations for some tests by hand, but that's not viable really.
>    * We also don't test for deleted entries between dir_iterator_advance() calls.
>    * Are my comments too much? Throughout git, .c files don't have many comments,
>    should I remove mine as well? I think they provide better context when reading
>    through the source code.
> 
> I do understand that it probably is too early to worry about most of these.
> However I wanted to communicate my thoughts and setup for the following
> versions.
> 
> While I wait for review, I'll implement/fix:
>    * DIR_ITERATOR_RECURSE proposed here[3], but with finer control. Instead of a
>    flag I'll introduce a new integer parameter in dir_iterator_begin(), which
>    will specify the maximum iteration depth.
>      * Supplying 0 will have the same behavior as DIR_ITERATOR_RECURSE i.e. it
>      will iterate over the entries of the root directory.
>      * Supplying -1 will iterate to maximum depth. This is the default right now.
>    * DIR_ITERATOR_DIRS_ONLY proposed here[4]. Enabling this, dir-iterator will
>    show only directories. Failing to enable DIR_ITERATOR_DIRS_BEFORE and/or
>    DIR_ITERATOR_DIRS_AFTER will result in dir_iterator_begin() returning NULL.
>    Is this a good way to encode "show only directories" in the flags?
> 
> I'll include them along with feedback and suggestions from this version in the
> next one.
> 
> I didn't refactor entry.c to use dir-iterator. It's a good first issue for
> someone else to become introduced to the community. I applied my patch[1] and it
> does not pass t/, as it used to, because of 15th test in t1092. Should I work on
> entry.c in my next version or leave it alone for a newcomer?
> 
> This serves as my microproject for GSoC. Could my future work on dir-iterator
> and cleanup of read_directory_recursive() and other customers of dir-iterator
> become a seperate GSoC project I could undertake?
> 
> [1]: https://public-inbox.org/git/20191208180439.19018-1-otalpster@gmail.com/
> [2]: https://public-inbox.org/git/1493226219-33423-1-git-send-email-bnmvco@gmail.com/
> [3]: https://public-inbox.org/git/CACsJy8DBa-oH3i+5P=iVr9NhJwsicZ43DO89WmvpYEQu90RrMw@mail.gmail.com/
> [4]: https://public-inbox.org/git/xmqqmvc265hk.fsf@gitster.mtv.corp.google.com/
> 
> Plato Kiorpelidis (6):
>    t0066: improve readablity of dir-iterator tests
>    t0066: better test coverage for dir-iterator
>    dir-iterator: refactor dir_iterator_advance()
>    dir-iterator: iterate dirs before or after their contents
>    t0066: remove redundant tests
>    test-dir-iterator: handle EACCES errno by dir-iterator
> 
>   builtin/clone.c              |    4 +-
>   dir-iterator.c               |  302 ++++++---
>   dir-iterator.h               |   34 +-
>   refs/files-backend.c         |    2 +-
>   t/helper/test-dir-iterator.c |   23 +-
>   t/t0066-dir-iterator.sh      | 1202 +++++++++++++++++++++++++++++++---
>   6 files changed, 1371 insertions(+), 196 deletions(-)
>