Subject: Re: [PATCH v4] clone: report duplicate entries on case-insensitive filesystems

From: Torsten Bögershausen <[email-masked]>
Date: Wed, 15 Aug 2018 21:08:16 +0200

On Sun, Aug 12, 2018 at 11:07:14AM +0200, Nguyễn Thái Ngọc Duy wrote:
> Paths that only differ in case work fine in a case-sensitive
> filesystems, but if those repos are cloned in a case-insensitive one,
> you'll get problems. The first thing to notice is "git status" will
> never be clean with no indication what exactly is "dirty".
> 
> This patch helps the situation a bit by pointing out the problem at
> clone time. Even though this patch talks about case sensitivity, the
> patch makes no assumption about folding rules by the filesystem. It
> simply observes that if an entry has been already checked out at clone
> time when we're about to write a new path, some folding rules are
> behind this.
> 
> This patch is tested with vim-colorschemes repository on a JFS partition
> with case insensitive support on Linux. This repository has two files
> darkBlue.vim and darkblue.vim.
> 
> Signed-off-by: Nguyễn Thái Ngọc Duy <[email-masked]>
> ---
>  v4 removes nr_duplicates (and fixes that false warning Szeder
>  reported). It also hints about case insensitivity as a cause of
>  problem because it's most likely the case when this warning shows up.
> 
>  builtin/clone.c  |  1 +
>  cache.h          |  1 +
>  entry.c          | 28 ++++++++++++++++++++++++++++
>  t/t5601-clone.sh |  8 +++++++-
>  unpack-trees.c   | 28 ++++++++++++++++++++++++++++
>  unpack-trees.h   |  1 +
>  6 files changed, 66 insertions(+), 1 deletion(-)
> 
> diff --git a/builtin/clone.c b/builtin/clone.c
> index 5c439f1394..0702b0e9d0 100644
> --- a/builtin/clone.c
> +++ b/builtin/clone.c
> @@ -747,6 +747,7 @@ static int checkout(int submodule_progress)
>  	memset(&opts, 0, sizeof opts);
>  	opts.update = 1;
>  	opts.merge = 1;
> +	opts.clone = 1;
>  	opts.fn = oneway_merge;
>  	opts.verbose_update = (option_verbosity >= 0);
>  	opts.src_index = &the_index;
> diff --git a/cache.h b/cache.h
> index 8b447652a7..6d6138f4f1 100644
> --- a/cache.h
> +++ b/cache.h
> @@ -1455,6 +1455,7 @@ struct checkout {
>  	unsigned force:1,
>  		 quiet:1,
>  		 not_new:1,
> +		 clone:1,
>  		 refresh_cache:1;
>  };
>  #define CHECKOUT_INIT { NULL, "" }
> diff --git a/entry.c b/entry.c
> index b5d1d3cf23..c70340df8e 100644
> --- a/entry.c
> +++ b/entry.c
> @@ -399,6 +399,31 @@ static int check_path(const char *path, int len, struct stat *st, int skiplen)
>  	return lstat(path, st);
>  }
>  
> +static void mark_colliding_entries(const struct checkout *state,
> +				   struct cache_entry *ce, struct stat *st)
> +{
> +	int i;
> +
> +	ce->ce_flags |= CE_MATCHED;
> +
> +#if !defined(GIT_WINDOWS_NATIVE) /* inode is always zero on Windows */
> +	for (i = 0; i < state->istate->cache_nr; i++) {
> +		struct cache_entry *dup = state->istate->cache[i];
> +
> +		if (dup == ce)
> +			break;
> +
> +		if (dup->ce_flags & (CE_MATCHED | CE_VALID | CE_SKIP_WORKTREE))
> +			continue;
> +

Should the following be protected by core.checkstat ? 
	if (check_stat) {

> +		if (dup->ce_stat_data.sd_ino == st->st_ino) {
> +			dup->ce_flags |= CE_MATCHED;
> +			break;
> +		}
> +	}
> +#endif

Another thing is that we switch of the ASCII case-folding-detection-logic
off for Windows users, even if we otherwise rely on icase.
I think we can use fspathcmp() as a fallback. when inodes fail,
because we may be on a network file system.
(I don't have a test setup at the moment, but what happens with inodes
when a Windows machine exports a share to Linux or Mac ?)

Is there a chance to get the fspathcmp() back, like this ?

static void mark_colliding_entries(const struct checkout *state,
				   struct cache_entry *ce, struct stat *st)
{
	int i;
	ce->ce_flags |= CE_MATCHED;

	for (i = 0; i < state->istate->cache_nr; i++) {
		struct cache_entry *dup = state->istate->cache[i];
		int folded = 0;

		if (dup == ce)
			break;

		if (dup->ce_flags & (CE_MATCHED | CE_VALID | CE_SKIP_WORKTREE))
			continue;

		if (!fspathcmp(dup->name, ce->name))
			folded = 1;

#if !defined(GIT_WINDOWS_NATIVE) /* inode is always zero on Windows */
		if (check_stat && (dup->ce_stat_data.sd_ino == st->st_ino))
			folded = 1;
#endif
		if (folded) {
			dup->ce_flags |= CE_MATCHED;
			break;
		}
	}
}