Make clear that equalFilePath does not expand ".."

Fixes #87

Author: hasufell

System/FilePath/Internal.hs

@@ -768,9 +768,12 @@ joinPath = foldr combine ""
 --   first this has a much better chance of working.
 --   Note that this doesn't follow symlinks or DOSNAM~1s.
 --
+-- Similar to 'normalise', this does not expand @".."@, because of symlinks.
+--
 -- >          x == y ==> equalFilePath x y
 -- >          normalise x == normalise y ==> equalFilePath x y
 -- >          equalFilePath "foo" "foo/"
+-- >          not (equalFilePath "/a/../c" "/c")
 -- >          not (equalFilePath "foo" "/foo")
 -- > Posix:   not (equalFilePath "foo" "FOO")
 -- > Windows: equalFilePath "foo" "FOO"

System/FilePath/Posix.hs

@@ -768,9 +768,12 @@ joinPath = foldr combine ""
 --   first this has a much better chance of working.
 --   Note that this doesn't follow symlinks or DOSNAM~1s.
 --
+-- Similar to 'normalise', this does not expand @".."@, because of symlinks.
+--
 -- >          x == y ==> equalFilePath x y
 -- >          normalise x == normalise y ==> equalFilePath x y
 -- >          equalFilePath "foo" "foo/"
+-- >          not (equalFilePath "/a/../c" "/c")
 -- >          not (equalFilePath "foo" "/foo")
 -- > Posix:   not (equalFilePath "foo" "FOO")
 -- > Windows: equalFilePath "foo" "FOO"

System/FilePath/Windows.hs

@@ -768,9 +768,12 @@ joinPath = foldr combine ""
 --   first this has a much better chance of working.
 --   Note that this doesn't follow symlinks or DOSNAM~1s.
 --
+-- Similar to 'normalise', this does not expand @".."@, because of symlinks.
+--
 -- >          x == y ==> equalFilePath x y
 -- >          normalise x == normalise y ==> equalFilePath x y
 -- >          equalFilePath "foo" "foo/"
+-- >          not (equalFilePath "/a/../c" "/c")
 -- >          not (equalFilePath "foo" "/foo")
 -- > Posix:   not (equalFilePath "foo" "FOO")
 -- > Windows: equalFilePath "foo" "FOO"

tests/TestGen.hs

@@ -359,6 +359,8 @@ tests =
     ,("W.normalise x == W.normalise y ==> W.equalFilePath x y", property $ \(QFilePath x) (QFilePath y) -> W.normalise x == W.normalise y ==> W.equalFilePath x y)
     ,("P.equalFilePath \"foo\" \"foo/\"", property $ P.equalFilePath "foo" "foo/")
     ,("W.equalFilePath \"foo\" \"foo/\"", property $ W.equalFilePath "foo" "foo/")
+    ,("not (P.equalFilePath \"/a/../c\" \"/c\")", property $ not (P.equalFilePath "/a/../c" "/c"))
+    ,("not (W.equalFilePath \"/a/../c\" \"/c\")", property $ not (W.equalFilePath "/a/../c" "/c"))
     ,("not (P.equalFilePath \"foo\" \"/foo\")", property $ not (P.equalFilePath "foo" "/foo"))
     ,("not (W.equalFilePath \"foo\" \"/foo\")", property $ not (W.equalFilePath "foo" "/foo"))
     ,("not (P.equalFilePath \"foo\" \"FOO\")", property $ not (P.equalFilePath "foo" "FOO"))