hgweb: ignore web.templates config when guessing mime type for static content

Frozen binaries won't have a file-system path for static content, so
I'd like to remove dependence on that. From the documentation, it
seems like `mimetypes.guess_type()` only cares about the suffix, so I
think it should be enough to pass in just path under the
`web.templates` directory.

Differential Revision: https://phab.mercurial-scm.org/D8935

mercurial/hgweb/common.py

@@ -201,7 +201,7 b' def staticfile(templatepath, directory, '
     try:
         os.stat(path)
         ct = pycompat.sysbytes(
-            mimetypes.guess_type(pycompat.fsdecode(path))[0] or r"text/plain"
+            mimetypes.guess_type(pycompat.fsdecode(fpath))[0] or r"text/plain"
         )
         with open(path, b'rb') as fh:
             data = fh.read()