bug#23595: 25.1.50; file with chinese/japanse chars, vc-diff fails (HG, Git, RCS)

[Paul Eggert]

On 05/23/2016 03:28 PM, Dmitry Gutov wrote:
> Does it have a bug report? Can we have a test case?

Not as far as I know. I was hoping we wouldn't have to write a bug 
report now, as emacs-25 does not have that bug now. I suppose someone 
with more free time could write a test case....

> > One idea to improve on the
> > current emacs-25 behavior is to test whether a simple ASCII message like
> > "Binary files differ" encodes as itself using the file's coding system,
> > and to use the file's coding system if it does and locale-coding-system
> > if it doesn't.
>
> How would we do that? We're currently picking conding-system-for-read 
> well before the first byte of the output is generated.

Emacs can decide the coding system before git diff generates any output, 
by applying decode-coding-string to a canary string sample. The attached 
patch should work; please give it a try.

0001-Fix-vc-diff-problems-with-UTF-16.patch
Description: Source code patch