I'm not convinced by [1c12ee9e45222d6c].  If I'm reading the patch correctly ..

If EEXIST is raised twice, TclFileMakeDirsCmd simply ignores it.  The comment above "goto nextPart" suggests something different, so I suspect this isn't intended.

Removing the call to FSStat means we can report success if the target exists and is a file.  This is clearly wrong.

Removing the Tcl_ResetResult() call rings alarm bells, but it looks like that was redundant in the first place.

I think lines 287-289 (post-patch) should simply be deleted so the success case can pass through Tcl_FSStat success on line 258.