Re: [WIP/RFC 00/23] repository object

> Glad to see you tackling this.  This is definitely a step in the
> right direction.
> 
> I realize that it will take a lot of work and that intermediate
> steps may just be pushing it the global state one level higher but
> eventually it would be great to see an entire code path global state
> free!
> 
> I'm personally interested because reducing the reliance on global
> state also helps us in our performance work as it makes it more
> possible to use threading to scale up the performance.

> 
> Ben
> 
> On 5/18/2017 7:21 PM, Brandon Williams wrote:
> >When I first started working on the git project I found it very difficult to
> >understand parts of the code base because of the inherently global nature of
> >our code.  It also made working on submodules very difficult.  Since we can
> >only open up a single repository per process, you need to launch a child
> >process in order to process a submodule.  But you also need to be able to
> >communicate other stateful information to the children processes so that the
> >submodules know how best to format their output or match against a
> >pathspec...it ends up feeling like layering on hack after hack.  What I would
> >really like to do, is to have the ability to have a repository object so that I
> >can open a submodule in-process.
> >
> >Before this becomes a reality for all commands, much of the library code would
> >need to be refactored in order to work purely on handles instead of global
> >state.  As it turned out, ls-files is a pretty simple command and doesn't have
> >*too* many dependencies.  The biggest thing that needed to be changed was
> >piping through an index into a couple library routines so that they don't
> >inherently rely on 'the_index'.  A few of these changes I've sent out and can
> >be found at 'origin/bw/pathspec-sans-the-index' and
> >'origin/bw/dir-c-stops-relying-on-the-index' which this series is based on.
> >
> >Patches 1-16 are refactorings to prepare either library code or ls-files itself
> >to be ready to handle passing around an index struct.  Patches 17-22 introduce
> >a repository struct and change a couple of things about how submodule caches
> >work (getting submodule information from .gitmodules).  And Patch 23 converts
> >ls-files to use a repository struct.
> >
> >The most interesting part of the series is from 17-23.  And 1-16 could be taken
> >as is without the rest of the series.
> >
> >This is still very much in a WIP state, though it does pass all tests.  What
> >I'm hoping for here is to get a discussion started about the feasibility of a
> >change like this and hopefully to get the ball rolling.  Is this a direction we
> >want to move in?  Is it worth the pain?
> >
> >Thanks for taking the time to look at this and entertain my insane ideas :)
> >
> >Brandon Williams (23):
> >  convert: convert get_cached_convert_stats_ascii to take an index
> >  convert: convert crlf_to_git to take an index
> >  convert: convert convert_to_git_filter_fd to take an index
> >  convert: convert convert_to_git to take an index
> >  convert: convert renormalize_buffer to take an index
> >  tree: convert read_tree to take an index parameter
> >  ls-files: convert overlay_tree_on_cache to take an index
> >  ls-files: convert write_eolinfo to take an index
> >  ls-files: convert show_killed_files to take an index
> >  ls-files: convert show_other_files to take an index
> >  ls-files: convert show_ru_info to take an index
> >  ls-files: convert ce_excluded to take an index
> >  ls-files: convert prune_cache to take an index
> >  ls-files: convert show_files to take an index
> >  ls-files: factor out debug info into a function
> >  ls-files: factor out tag calculation
> >  repo: introduce new repository object
> >  repo: add index_state to struct repo
> >  repo: add per repo config
> >  submodule-config: refactor to allow for multiple submodule_cache's
> >  repo: add repo_read_gitmodules
> >  submodule: add is_submodule_active
> >  ls-files: use repository object
> >
> > Makefile                               |   1 +
> > apply.c                                |   2 +-
> > builtin/blame.c                        |   2 +-
> > builtin/commit.c                       |   3 +-
> > builtin/ls-files.c                     | 348 ++++++++++++++++-----------------
> > cache.h                                |   4 +-
> > combine-diff.c                         |   2 +-
> > config.c                               |   2 +-
> > convert.c                              |  31 +--
> > convert.h                              |  19 +-
> > diff.c                                 |   6 +-
> > dir.c                                  |   2 +-
> > git.c                                  |   2 +-
> > ll-merge.c                             |   2 +-
> > merge-recursive.c                      |   4 +-
> > repo.c                                 | 112 +++++++++++
> > repo.h                                 |  22 +++
> > sha1_file.c                            |   6 +-
> > submodule-config.c                     |  40 +++-
> > submodule-config.h                     |  10 +
> > submodule.c                            |  51 +++++
> > submodule.h                            |   2 +
> > t/t3007-ls-files-recurse-submodules.sh |  39 ++++
> > tree.c                                 |  28 ++-
> > tree.h                                 |   3 +-
> > 25 files changed, 513 insertions(+), 230 deletions(-)
> > create mode 100644 repo.c
> > create mode 100644 repo.h
> >