Subject: Re: [PATCH v2 1/3] repository: fix repo_read_index with submodules

From: Thomas Gummerer <[email-masked]>
Date: Mon, 18 Dec 2017 23:05:11 +0000

On 12/18, Brandon Williams wrote:
> On 12/17, Thomas Gummerer wrote:
> > repo_read_index calls read_index_from, which takes an path argument for
> > the location of the index file.  For the split index however it relies
> 
> > on the current working directory to construct the path using git_path.
> 
> This line isn't actually true and should probably be fixed.  git_path
> doesn't rely on the CWD but rather it relies on the gitdir of the main
> repository (the_repository).

Right, let me fix that.  Thanks!

> > 
> > repo_read_index calls read_index_from with the full path for the index
> > file, however it doesn't change the cwd, so when split index mode is
> > turned on, read_index_from can't find the file for the split index.
> > 
> > For example t3007-ls-files-recurse-submodules.sh was broken with
> > GIT_TEST_SPLIT_INDEX set in 188dce131f ("ls-files: use repository
> > object", 2017-06-22), and t7814-grep-recurse-submodules.sh was also
> > broken in a similar manner, probably by introducing struct repository
> > there, although I didn't track down the exact commit for that.
> > 
> > Fix this by introducing a new read_index_for_repo function, which knows
> > about the correct paths for the submodules.
> > 
> > The alternative would have been to make the callers pass in the base
> > path for the split index, however that ended up being more complicated,
> > and I think we want to converge towards using struct repository for
> > things like these anyway.
> > 
> > Signed-off-by: Thomas Gummerer <[email-masked]>
> > ---
> >  cache.h      |  1 +
> >  read-cache.c | 16 ++++++++++++++--
> >  repository.c |  2 +-
> >  3 files changed, 16 insertions(+), 3 deletions(-)
> > 
> > diff --git a/cache.h b/cache.h
> > index cb5db7bf83..d42bea1ef7 100644
> > --- a/cache.h
> > +++ b/cache.h
> > @@ -614,6 +614,7 @@ extern int read_index_preload(struct index_state *, const struct pathspec *paths
> >  extern int do_read_index(struct index_state *istate, const char *path,
> >  			 int must_exist); /* for testting only! */
> >  extern int read_index_from(struct index_state *, const char *path);
> > +extern int read_index_for_repo(const struct repository *);
> >  extern int is_index_unborn(struct index_state *);
> >  extern int read_index_unmerged(struct index_state *);
> >  
> > diff --git a/read-cache.c b/read-cache.c
> > index 2eb81a66b9..70357febdc 100644
> > --- a/read-cache.c
> > +++ b/read-cache.c
> > @@ -20,6 +20,7 @@
> >  #include "split-index.h"
> >  #include "utf8.h"
> >  #include "fsmonitor.h"
> > +#include "repository.h"
> >  
> >  /* Mask for the name length in ce_flags in the on-disk index */
> >  
> > @@ -1871,7 +1872,8 @@ static void freshen_shared_index(char *base_sha1_hex, int warn)
> >  	free(shared_index);
> >  }
> >  
> > -int read_index_from(struct index_state *istate, const char *path)
> > +static int do_read_index_from(struct index_state *istate, const char *path,
> > +			      const struct repository *repo)
> >  {
> >  	struct split_index *split_index;
> >  	int ret;
> > @@ -1896,7 +1898,7 @@ 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 = repo_git_path(repo, "sharedindex.%s", 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",
> > @@ -1909,6 +1911,16 @@ int read_index_from(struct index_state *istate, const char *path)
> >  	return ret;
> >  }
> >  
> > +int read_index_for_repo(const struct repository *repo)
> > +{
> > +	return do_read_index_from(repo->index, repo->index_file, repo);
> > +}
> 
> > +
> > +int read_index_from(struct index_state *istate, const char *path)
> > +{
> > +	return do_read_index_from(istate, path, the_repository);
> > +}
> 
> This looks fine, though I wonder what the point of passing in the index
> file even was since we end just ended up reading the 'sharedindex' file based
> on the git path. I'm just curious about how this function evolved.

There are some callsites that are using an index different form
$gitdir/index, or even GIT_INDEX_FILE.  e.g. see builtin/am.c [*1*],
which uses it's own 'patch-merge-index' in the am state directory for
its internal operations.

The split index mode was later bolted on, and the sharedindex.xxxx
would always go in $gitdir for the repository.  Others probably know
quite a bit more about this, while I'm always interested in index
related things as that's how I got started with the git project, I
couldn't follow all the conversations that were going on there.

*1*: https://github.com/gitster/git/blob/52015aaf9d19c97b52c47c7046058e6d029ff856/builtin/am.c#L1844

> > +
> >  int is_index_unborn(struct index_state *istate)
> >  {
> >  	return (!istate->cache_nr && !istate->timestamp.sec);
> > diff --git a/repository.c b/repository.c
> > index bb2fae5446..928b1f553d 100644
> > --- a/repository.c
> > +++ b/repository.c
> > @@ -229,5 +229,5 @@ int repo_read_index(struct repository *repo)
> >  	if (!repo->index)
> >  		repo->index = xcalloc(1, sizeof(*repo->index));
> >  
> > -	return read_index_from(repo->index, repo->index_file);
> > +	return read_index_for_repo(repo);
> >  }
> > -- 
> > 2.15.1.620.gb9897f4670
> > 
> 
> -- 
> Brandon Williams