relative_to, proximate_to, is_subdir: emit warning if '..' component of input

this is ambiguous and different libraries handle this including incorrectly
python.pathlib, C++ <filesystem>, java implementations,...

Author: scivision

+stdlib/is_subdir.m

@@ -6,12 +6,19 @@
   dir (1,1) string
 end
 
+
 if ischar(subdir)
-  s = strfind(subdir, dir) == 1 && (length(subdir) > length(dir)); %#ok<UNRCH>
+  w = ~isempty(strfind(dir, "..")) || ~isempty(strfind(subdir, "..")); %#ok<STREMP,UNRCH>
+  s = strfind(subdir, dir) == 1 && (length(subdir) > length(dir));
 else
+  w = contains(dir, "..") || contains(subdir, "..");
   s = startsWith(subdir, dir) && (strlength(subdir) > strlength(dir));
 end
 
+if ~strcmp(subdir, dir) && w
+  warning("is_subdir: %s and/or %s is ambiguous input with '..'  consider using stdlib.canonical() first", subdir, dir)
+end
+
 end
 
 %!assert(!is_subdir("/a/b", "/a/b"))
@@ -21,4 +28,4 @@
 %!assert(is_subdir("a/b", "a"))
 %!assert(!is_subdir("a", "a/.c"))
 
-% this is incorrect on Windows at least%assert(is_subdir("a/b", "a/b/.."))
+% this is incorrect on Windows at least %assert(is_subdir("a/b", "a/b/.."))

+stdlib/relative_to.m

@@ -16,13 +16,19 @@
 end
 
 if stdlib.isoctave()
+  w = ~isempty(strfind(b1, "..")); %#ok<STREMP>
   b = javaObject("java.io.File", b1).toPath();
   o = javaObject("java.io.File", o1).toPath();
 else
+  w = contains(b1, "..");
   b = java.io.File(b1).toPath();
   o = java.io.File(o1).toPath();
 end
 
+if w
+  warning("relative_to(%s) is ambiguous base with '..'  consider using stdlib.canonical() first", b1)
+end
+
 try
   r = stdlib.posix(b.relativize(o).toString());
 catch e

test/TestFilePure.m

@@ -92,7 +92,7 @@
 {"/a/b", "/a", ".."}, ...
 {"/a/b/c/d", "/a/b", "../.."}, ...
 {"this/one", "this/two", "../two"}};
-% NOTE: ".." in relative_to is ambiguous including for python.pathlib, C++ <filesystem>, etc.
+% NOTE: ".." in relative_to(base) is ambiguous including for python.pathlib, C++ <filesystem>, etc.
 
 p_proximate_to = p_relative_to;
 
@@ -111,7 +111,7 @@
 {"c:/path", "d:/path", ""}}];
 
 p_proximate_to = p_relative_to;
-% NOTE: ".." in proximate_to is ambiguous including for python.pathlib, C++ <filesystem>, etc
+% NOTE: ".." in proximate_to(base) is ambiguous including for python.pathlib, C++ <filesystem>, etc
 
 p_proximate_to{6}{3} = "/";
 p_proximate_to{10}{3} = "c";
@@ -156,7 +156,7 @@
   {"a/b", "a", true}, ...
   {"a/.c", "a", true}
 };
-% NOTE: ".." in is_subidr is ambiguous
+% NOTE: ".." in is_subdir (either argument) is ambiguous
 
 if ispc
   p_is_subdir{end+1} = {"c:\", "c:/", false};