Subject: Re: [PATCH v2 2/3] prune: fix pruning with multiple worktrees and split index

From: Thomas Gummerer <[email-masked]>
Date: Wed, 3 Jan 2018 22:18:49 +0000

[sorry for the late reply.  I was on Christmas holidays until today
and am still catching up on the mailing list.  It will probably take
me untill the weekend to send a re-roll]

On 12/18, Brandon Williams wrote:
> On 12/17, Thomas Gummerer wrote:
> > be489d02d2 ("revision.c: --indexed-objects add objects from all
> > worktrees", 2017-08-23) made sure that pruning takes objects from all
> > worktrees into account.
> > 
> > It did that by reading the index of every worktree and adding the
> > necessary index objects to the set of pending objects.  The index is
> > read by read_index_from.  As mentioned in the previous commit,
> > read_index_from depends on the CWD for the location of the split index,
> 
> As I mentioned before this doesn't actually depend on the CWD but
> rather the per-worktree gitdir.

Right, will fix.

> > and add_index_objects_to_pending doesn't set that before using
> > read_index_from.
> > 
> > Instead of using read_index_from, use repo_read_index, which is aware of
> > the proper paths for the worktree.
> > 
> > This fixes t5304-prune when ran with GIT_TEST_SPLIT_INDEX set.
> > 
> > Signed-off-by: Thomas Gummerer <[email-masked]>
> > ---
> >  repository.c | 11 +++++++++++
> >  repository.h |  2 ++
> >  revision.c   | 14 +++++++++-----
> >  3 files changed, 22 insertions(+), 5 deletions(-)
> > 
> > diff --git a/repository.c b/repository.c
> > index 928b1f553d..3c9bfbd1b8 100644
> > --- a/repository.c
> > +++ b/repository.c
> > @@ -2,6 +2,7 @@
> >  #include "repository.h"
> >  #include "config.h"
> >  #include "submodule-config.h"
> > +#include "worktree.h"
> >  
> >  /* The main repository */
> >  static struct repository the_repo = {
> > @@ -146,6 +147,16 @@ int repo_init(struct repository *repo, const char *gitdir, const char *worktree)
> >  	return -1;
> >  }
> >  
> > +/*
> > + * Initialize 'repo' based on the provided worktree
> > + * Return 0 upon success and a non-zero value upon failure.
> > + */
> > +int repo_worktree_init(struct repository *repo, struct worktree *worktree)
> > +{
> > +	return repo_init(repo, get_worktree_git_dir(worktree),
> > +			 worktree->path);
> 
> I still feel very unsettled about this and don't think its a good idea.
> get_worktree_git_dir depends implicitly on the global the_repository
> object and I would like to avoid relying on it for an initialization
> function like this.
> 
> > +}
> > +
> >  /*
> >   * Initialize 'submodule' as the submodule given by 'path' in parent repository
> >   * 'superproject'.
> > diff --git a/repository.h b/repository.h
> > index 7f5e24a0a2..2adeb05bf4 100644
> > --- a/repository.h
> > +++ b/repository.h
> > @@ -4,6 +4,7 @@
> >  struct config_set;
> >  struct index_state;
> >  struct submodule_cache;
> > +struct worktree;
> >  
> >  struct repository {
> >  	/* Environment */
> > @@ -87,6 +88,7 @@ extern struct repository *the_repository;
> >  extern void repo_set_gitdir(struct repository *repo, const char *path);
> >  extern void repo_set_worktree(struct repository *repo, const char *path);
> >  extern int repo_init(struct repository *repo, const char *gitdir, const char *worktree);
> > +extern int repo_worktree_init(struct repository *repo, struct worktree *worktree);
> >  extern int repo_submodule_init(struct repository *submodule,
> >  			       struct repository *superproject,
> >  			       const char *path);
> > diff --git a/revision.c b/revision.c
> > index e2e691dd5a..34e1e4b799 100644
> > --- a/revision.c
> > +++ b/revision.c
> > @@ -22,6 +22,7 @@
> >  #include "packfile.h"
> >  #include "worktree.h"
> >  #include "argv-array.h"
> > +#include "repository.h"
> >  
> >  volatile show_early_output_fn_t show_early_output;
> >  
> > @@ -1346,15 +1347,18 @@ void add_index_objects_to_pending(struct rev_info *revs, unsigned int flags)
> >  	worktrees = get_worktrees(0);
> >  	for (p = worktrees; *p; p++) {
> >  		struct worktree *wt = *p;
> > -		struct index_state istate = { NULL };
> > +		struct repository *repo;
> >  
> > +		repo = xmalloc(sizeof(struct repository));
> >  		if (wt->is_current)
> >  			continue; /* current index already taken care of */
> > +		if (repo_worktree_init(repo, wt))
> > +			BUG("couldn't initialize repository object from worktree");
> >  
> > -		if (read_index_from(&istate,
> > -				    worktree_git_path(wt, "index")) > 0)
> 
> Ok, after thinking this through a bit more I think a better approach may
> be to restructure the call to read_index_from to take in both an index
> file as well as the explicit gitdir to use when constructing a path to
> the sharedindex file.  That way you can fix this for worktrees and
> submodules without having to pass in a repository object to the logic
> which is reading an index file as well as avoiding needing to init a
> repository object for every worktree.

I still think with eventually we probably only want to read the index
through a repository object instead of reading it to a separate struct
index_state.

But we can probably defer that for now, as this series really just
wants to fix the regressions, and we can think a bit more about how
the repository struct interacts with worktrees.

> So you could rework the first patch to do something like:

Thanks for the below, I'll try the below and see how much churn it
causes adjusting all the callsites, and send a re-roll later this
week.

> diff --git a/read-cache.c b/read-cache.c
> index 2eb81a66b..3a04b5567 100644
> --- a/read-cache.c
> +++ b/read-cache.c
> @@ -1863,20 +1863,19 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
>   * This way, shared index can be removed if they have not been used
>   * for some time.
>   */
> -static void freshen_shared_index(char *base_sha1_hex, int warn)
> +static void freshen_shared_index(const char *shared_index, int warn)
>  {
> -	char *shared_index = git_pathdup("sharedindex.%s", base_sha1_hex);
>  	if (!check_and_freshen_file(shared_index, 1) && warn)
>  		warning("could not freshen shared index '%s'", shared_index);
> -	free(shared_index);
>  }
>  
> -int read_index_from(struct index_state *istate, const char *path)
> +int read_index_from(struct index_state *istate, const char *path,
> +		    const char *gitdir)
>  {
>  	struct split_index *split_index;
>  	int ret;
>  	char *base_sha1_hex;
> -	const char *base_path;
> +	char *base_path;
>  
>  	/* istate->initialized covers both .git/index and .git/sharedindex.xxx */
>  	if (istate->initialized)
> @@ -1896,14 +1895,14 @@ int read_index_from(struct index_state *istate, const char *path)
>  		split_index->base = xcalloc(1, sizeof(*split_index->base));
>  
>  	base_sha1_hex = sha1_to_hex(split_index->base_sha1);
> -	base_path = git_path("sharedindex.%s", base_sha1_hex);
> +	base_path = xstrfmt("%s/sharedindex.%s", gitdir, base_sha1_hex);
>  	ret = do_read_index(split_index->base, base_path, 1);
>  	if (hashcmp(split_index->base_sha1, split_index->base->sha1))
>  		die("broken index, expect %s in %s, got %s",
>  		    base_sha1_hex, base_path,
>  		    sha1_to_hex(split_index->base->sha1));
>  
> -	freshen_shared_index(base_sha1_hex, 0);
> +	freshen_shared_index(base_path, 0);
>  	merge_base_index(istate);
>  	post_read_index_from(istate);
> + free(base_path);
>  	return ret;
> 
> 
> -- 
> Brandon Williams