Emacs fails to recogize "iso-2022-jp" encoded file

[Miles Bader]

VIsiting a file which is encoded using the "iso-2022-jp" coding system,
using the command ("/tmp/isojp" is the file):

   LANG=ja_JP.utf-8 emacs -Q /tmp/isojp

... does not recognize the file's encoding properly, and instead tries
to decode it using utf-8 (so the file contents show up as a bunch of
escape characters).

Emacs reads the file properly if the encoding to use is explicitly
specified (with "C-x C-m c iso-2022-jp RET C-x C-f").

This worked properly as of a week or so ago (not sure the exact dates),
so it seems to be a recent regression.

Thanks,

-Miles

p.s. I've attached the test file I used, though it seems to happen with
any iso-2022-jp encoded file.

isojp
Description: test file for emacs

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