bug#5297: [PATCH] vc: fixed test of symlinks on abbreviatable path

[Chong Yidong]

Yuya Nishihara <yuya@tcha.org> writes:

>     vc: fixed test of symlinks on abbreviatable path
>     
>     buffer-file-truename is *abbreviated* truename, but
>     buffer-file-name seems not, so we need to expand it.
>     
>     With abbreviated file-name, at least, vc-git and vc-hg are not detected
>     as backend. This means symlinks to git/hg-managed files on HOME directory
>     are not handled by vc-find-file-hook.

Sorry for the long delay.  I didn't have a test case, but this patch
looks correct so I've installed it in trunk.