Re: [PATCH v2 14/16] fsmonitor: support case-insensitive events

> +/*
> + * Use the name-hash to do a case-insensitive cache-entry lookup with
> + * the pathname and invalidate the cache-entry.
> + *
> + * Returns the number of cache-entries that we invalidated.
> + */
> +static size_t handle_using_name_hash_icase(
> +	struct index_state *istate, const char *name)
> +{
> +	struct cache_entry *ce = NULL;
> +
> +	ce = index_file_exists(istate, name, strlen(name), 1);
> +	if (!ce)
> +		return 0;
> +
> +	/*
> +	 * A case-insensitive search in the name-hash using the
> +	 * observed pathname found a cache-entry, so the observed path
> +	 * is case-incorrect.  Invalidate the cache-entry and use the
> +	 * correct spelling from the cache-entry to invalidate the
> +	 * untracked-cache.  Since we now have sparse-directories in
> +	 * the index, the observed pathname may represent a regular
> +	 * file or a sparse-index directory.
> +	 *
> +	 * Note that we should not have seen FSEvents for a
> +	 * sparse-index directory, but we handle it just in case.
> +	 *
> +	 * Either way, we know that there are not any cache-entries for
> +	 * children inside the cone of the directory, so we don't need to
> +	 * do the usual scan.
> +	 */
> +	trace_printf_key(&trace_fsmonitor,
> +			 "fsmonitor_refresh_callback MAP: '%s' '%s'",
> +			 name, ce->name);
> +
> +	untracked_cache_invalidate_trimmed_path(istate, ce->name, 0);
> +	ce->ce_flags &= ~CE_FSMONITOR_VALID;
> +	return 1;
> +}

> +
> +/*
> + * Use the dir-name-hash to find the correct-case spelling of the
> + * directory.  Use the canonical spelling to invalidate all of the
> + * cache-entries within the matching cone.
> + *
> + * Returns the number of cache-entries that we invalidated.
> + */
> +static size_t handle_using_dir_name_hash_icase(
> +	struct index_state *istate, const char *name)

> +{
> +	struct strbuf canonical_path = STRBUF_INIT;
> +	int pos;
> +	size_t len = strlen(name);
> +	size_t nr_in_cone;
> +
> +	if (name[len - 1] == '/')
> +		len--;
> +
> +	if (!index_dir_find(istate, name, len, &canonical_path))
> +		return 0; /* name is untracked */
> +
> +	if (!memcmp(name, canonical_path.buf, canonical_path.len)) {
> +		strbuf_release(&canonical_path);
> +		/*
> +		 * NEEDSWORK: Our caller already tried an exact match
> +		 * and failed to find one.  They called us to do an
> +		 * ICASE match, so we should never get an exact match,
> +		 * so we could promote this to a BUG() here if we
> +		 * wanted to.  It doesn't hurt anything to just return
> +		 * 0 and go on becaus we should never get here.  Or we
> +		 * could just get rid of the memcmp() and this "if"
> +		 * clause completely.
> +		 */
> +		return 0; /* should not happen */
> +	}

> +
> +	trace_printf_key(&trace_fsmonitor,
> +			 "fsmonitor_refresh_callback MAP: '%s' '%s'",
> +			 name, canonical_path.buf);
> +
> +	/*
> +	 * The dir-name-hash only tells us the corrected spelling of
> +	 * the prefix.  We have to use this canonical path to do a
> +	 * lookup in the cache-entry array so that we repeat the
> +	 * original search using the case-corrected spelling.
> +	 */
> +	strbuf_addch(&canonical_path, '/');
> +	pos = index_name_pos(istate, canonical_path.buf,
> +			     canonical_path.len);
> +	nr_in_cone = handle_path_with_trailing_slash(
> +		istate, canonical_path.buf, pos);
> +	strbuf_release(&canonical_path);
> +	return nr_in_cone;
> +}

> @@ -319,6 +416,19 @@ static void fsmonitor_refresh_callback(struct index_state *istate, char *name)
>  	else
>  		nr_in_cone = handle_path_without_trailing_slash(istate, name, pos);
>  
> +	/*
> +	 * If we did not find an exact match for this pathname or any
> +	 * cache-entries with this directory prefix and we're on a
> +	 * case-insensitive file system, try again using the name-hash
> +	 * and dir-name-hash.
> +	 */
> +	if (!nr_in_cone && ignore_case) {
> +		nr_in_cone = handle_using_name_hash_icase(istate, name);
> +		if (!nr_in_cone)
> +			nr_in_cone = handle_using_dir_name_hash_icase(
> +				istate, name);
> +	}