Add Path#empty?

spec/std/path_spec.cr

@@ -727,4 +727,14 @@ describe Path do
     assert_paths_raw("foo/bar", Path.posix("foo/bar"), &.to_posix)
     assert_paths_raw("C:\\foo\\bar", Path.posix("C:\\foo\\bar"), Path.posix("C:/foo/bar"), &.to_posix)
   end
+
+  describe "#empty?" do
+    assert_paths_raw("", true, &.empty?)
+    assert_paths_raw(".", true, &.empty?)
+    assert_paths_raw("./", false, &.empty?)
+    assert_paths_raw("a", false, &.empty?)
+    assert_paths_raw("a/b", false, &.empty?)
+    assert_paths_raw("..", false, &.empty?)
+    assert_paths_raw("/", false, &.empty?)
+  end
 end

src/path.cr

@@ -9,8 +9,8 @@
 # A `Path` can represent a root, a root and a sequence of names, or simply one or
 # more name elements.
 # A `Path` is considered to be an empty path if it consists solely of one name
-# element that is empty. Accessing a file using an empty path is equivalent
-# to accessing the default directory of the process.
+# element that is empty or equal to `"."`. Accessing a file using an empty path
+# is equivalent to accessing the default directory of the process.
 #
 # # Examples
 #
@@ -230,7 +230,7 @@ struct Path
 
   # Returns the parent path of this path.
   #
-  # If the path is empty or `"."`, it returns `"."`. If the path is rooted
+  # If the path is empty, it returns `"."`. If the path is rooted
   # and in the top-most hierarchy, the root path is returned.
   #
   # ```
@@ -267,7 +267,7 @@ struct Path
   # # Path["foo/bar"]
   # ```
   def each_parent(&block : Path ->)
-    return if @name.empty? || @name == "."
+    return if empty?
 
     first_char = @name.char_at(0)
     unless separators.includes?(first_char) || (first_char == '.' && separators.includes?(@name.byte_at?(1).try &.unsafe_chr)) || (windows? && (windows_drive? || unc_share?))
@@ -398,7 +398,7 @@ struct Path
   #
   # See also Rob Pike: *[Lexical File Names in Plan 9 or Getting Dot-Dot Right](https://9p.io/sys/doc/lexnames.html)*
   def normalize(*, remove_final_separator : Bool = true) : Path
-    return new_instance "." if @name.empty?
+    return new_instance "." if empty?
 
     drive, root = drive_and_root
     reader = Char::Reader.new(@name)
@@ -869,6 +869,20 @@ struct Path
     end
   end
 
+  # Returns `true` if this path is empty.
+  #
+  # `Path[""]` and `Path["."]` are considered empty.
+  #
+  # ```
+  # Path[""].empty?  # => true
+  # Path["."].empty? # => true
+  # Path["a"].empty? # => false
+  # Path["/"].empty? # => false
+  # ```
+  def empty?
+    @name.empty? || @name == "."
+  end
+
   # Compares this path to *other*.
   #
   # The comparison is performed strictly lexically: `foo` and `./foo` are *not*