Fix add_dir() in the case of symlinks to hidden directories

add_dir() tries to ignore symlinks that point within directory being added
(since those files would be added anyway). Unfortunately, it failed to account
for the case of symlinks that point to *hidden* files within directory being
added.

On Mon, Apr 22, 2013 at 9:37 PM, Markus Rothe <markus@unixforces.net> wrote:
> On Mon, Apr 22, 2013 at 04:13:57PM +0400, Gregory Petrosyan wrote:
>> Can you please simplify the test case — try to repeat adding the
>> music, but e.g. one directory containing one (symlinked) file, and go
>> from there?
>
> You are correct. I also discovered that adding symlinked files works in
> some cases. But here is a minimal testcase, which I cannot add by
> running ":add ~/tmp/music/"; i.e. no files are added.
>
>     % tree ~/tmp/music -aN
>     /home/markus/tmp/music
>     |-- .content
>     |   `-- 01 - Speak To Me - Breathe In The Air.flac
>     `-- Pink Floyd
>         `-- 1973 - The Dark Side Of The Moon
>             `-- 01 - Speak To Me - Breathe In The Air.flac -> ../../.content/01 - Speak To Me - Breathe In The Air.flac
>
>     3 directories, 2 files
>
> [ .content would be .git in my case ]
>
> Note that I *can* add it using ":add ~/tmp/music/Pink Floyd/".

Reported-by: Markus Rothe <markus@unixforces.net>
Signed-off-by: Gregory Petrosyan <gregory.petrosyan@gmail.com>