Fix directory-existence check on Windows

This fixes a bug on Windows where `fd` could not be used on ram disks
and encrypted folders.

closes #752

Cargo.lock

@@ -1,5 +1,7 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+version = 3
+
 [[package]]
 name = "aho-corasick"
 version = "0.7.18"
@@ -166,6 +168,7 @@ dependencies = [
  "lazy_static",
  "libc",
  "lscolors",
+ "normpath",
  "num_cpus",
  "regex",
  "regex-syntax",
@@ -330,6 +333,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "normpath"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "27e6e8f70e9fbbe3752d330d769e3424f24b9458ce266df93a3b456902fd696a"
+dependencies = [
+ "winapi",
+]
+
 [[package]]
 name = "num_cpus"
 version = "1.13.0"

Cargo.toml

@@ -47,6 +47,7 @@ lscolors = "0.7"
 globset = "0.4"
 anyhow = "1.0"
 dirs-next = "2.0"
+normpath = "0.3"
 
 [dependencies.clap]
 version = "2.31.2"

src/filesystem.rs

@@ -7,6 +7,8 @@ use std::io;
 use std::os::unix::fs::{FileTypeExt, PermissionsExt};
 use std::path::{Path, PathBuf};
 
+use normpath::PathExt;
+
 use crate::walk;
 
 pub fn path_absolute_form(path: &Path) -> io::Result<PathBuf> {
@@ -33,10 +35,10 @@ pub fn absolute_path(path: &Path) -> io::Result<PathBuf> {
     Ok(path_buf)
 }
 
-// Path::is_dir() is not guaranteed to be intuitively correct for "." and ".."
-// See: https://github.com/rust-lang/rust/issues/45302
-pub fn is_dir(path: &Path) -> bool {
-    path.is_dir() && (path.file_name().is_some() || path.canonicalize().is_ok())
+pub fn is_existing_directory(path: &Path) -> bool {
+    // Note: we do not use `.exists()` here, as `.` always exists, even if
+    // the CWD has been deleted.
+    path.is_dir() && (path.file_name().is_some() || path.normalize().is_ok())
 }
 
 #[cfg(any(unix, target_os = "redox"))]

src/main.rs

@@ -55,7 +55,7 @@ fn run() -> Result<ExitCode> {
     // Set the current working directory of the process
     if let Some(base_directory) = matches.value_of_os("base-directory") {
         let base_directory = Path::new(base_directory);
-        if !filesystem::is_dir(base_directory) {
+        if !filesystem::is_existing_directory(base_directory) {
             return Err(anyhow!(
                 "The '--base-directory' path '{}' is not a directory.",
                 base_directory.to_string_lossy()
@@ -70,7 +70,7 @@ fn run() -> Result<ExitCode> {
     }
 
     let current_directory = Path::new(".");
-    if !filesystem::is_dir(current_directory) {
+    if !filesystem::is_existing_directory(current_directory) {
         return Err(anyhow!(
             "Could not retrieve current directory (has it been deleted?)."
         ));
@@ -95,7 +95,7 @@ fn run() -> Result<ExitCode> {
         let mut directories = vec![];
         for path in paths {
             let path_buffer = PathBuf::from(path);
-            if filesystem::is_dir(&path_buffer) {
+            if filesystem::is_existing_directory(&path_buffer) {
                 directories.push(path_buffer);
             } else {
                 print_error(format!(
@@ -130,7 +130,7 @@ fn run() -> Result<ExitCode> {
     // Detect if the user accidentally supplied a path instead of a search pattern
     if !matches.is_present("full-path")
         && pattern.contains(std::path::MAIN_SEPARATOR)
-        && filesystem::is_dir(Path::new(pattern))
+        && Path::new(pattern).is_dir()
     {
         return Err(anyhow!(
             "The search pattern '{pattern}' contains a path-separation character ('{sep}') \