When the virtualfilesystem is enabled the previous implementation of
clear_ce_flags would iterate all of the cache entries and query whether
each one is in the virtual filesystem to determine whether to clear one
of the SKIP_WORKTREE bits. For each cache entry, we would do a hash
lookup for each parent directory in the is_included_in_virtualfilesystem
function.
The former approach is slow for a typical Windows OS enlistment with
3 million files where only a small percentage is in the virtual
filesystem. The cost is
O(n_index_entries * n_chars_per_path * n_parent_directories_per_path).
In this change, we use the same approach as apply_virtualfilesystem,
which iterates the set of entries in the virtualfilesystem and searches
in the cache for the corresponding entries in order to clear their
flags. This approach has a cost of
O(n_virtual_filesystem_entries * n_chars_per_path * log(n_index_entries)).
The apply_virtualfilesystem code was refactored a bit and modified to
clear flags for all names that 'alias' a given virtual filesystem name
when ignore_case is set.
n_virtual_filesystem_entries is typically much less than
n_index_entries, in which case the new approach is much faster. We wind
up building the name hash for the index, but this occurs quickly thanks
to the multi-threading.
Signed-off-by: Neeraj Singh <neerajsi@ntdev.microsoft.com>
index_dir_exists() returns a boolean to indicate if there is a
case-insensitive match in the directory name-hash, but does not
provide the caller with the exact spelling of that match.
Create index_dir_find() to do the case-insensitive search *and*
optionally return the spelling of the matched directory prefix in a
provided strbuf.
To avoid code duplication, convert index_dir_exists() to be a trivial
wrapper around the new index_dir_find().
Signed-off-by: Jeff Hostetler <jeffhostetler@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Neeraj Singh
Jeff Hostetler
Elijah Newren