ignore: upgrade to walkdir 2

The uninteresting bits of this commit involve mechanical changes for
updates to walkdir 2. The more interesting bits of this commit are the
breaking changes, although none of them should require any significant
change on users of this library. The breaking changes are as follows:

* `DirEntry::path_is_symbolic_link` has been renamed to
  `DirEntry::path_is_symlink`. This matches the conventions in the
  standard library, and also the corresponding name change in walkdir.
* Removed the `From<walkdir::Error> for ignore::Error` impl. This was
  intended to only be used internally, but was the only thing that
  made `walkdir` a public dependency of `ignore`. Therefore, we remove
  it since it seems unnecessary.
* Renamed `WalkBuilder::sort_by` to `WalkBuilder::sort_by_file_name`,
  and changed the type of the comparator from

    Fn(&OsString, &OsString) -> cmp::Ordering + 'static

  to

    Fn(&OsStr, &OsStr) -> cmp::Ordering + Send + Sync + 'static

  The corresponding change in `walkdir` retains the `sort_by` name, but
  gives the comparator a pair of `&DirEntry` values instead of a pair
  of `&OsStr` values. Ideally, `ignore` would hand off its own pair of
  `&ignore::DirEntry` values, but this requires more design work. So for
  now, we retain previous functionality, but leave room to make a proper
  `sort_by` method.

[breaking-change]

1 files changed, 1 insertions, 1 deletions

diff --git a/src/args.rs b/src/args.rs
index ff636d17..5d2e6880 100644
--- a/src/args.rs
+++ b/src/args.rs
@@ -287,7 +287,7 @@ impl Args {
         wd.parents(!self.no_ignore_parent);
         wd.threads(self.threads());
         if self.sort_files {
-            wd.sort_by(|a, b| a.cmp(b));
+            wd.sort_by_file_name(|a, b| a.cmp(b));
         }
         wd
     }