config, gitignore: failure to access with ENOTDIR is ok

config, gitignore: failure to access with ENOTDIR is ok

The access_or_warn() function is used to check for optional
configuration files like .gitconfig and .gitignore and warn when they
are not accessible due to a configuration issue (e.g., bad
permissions).  It is not supposed to complain when a file is simply
missing.

Noticed on a system where ~/.config/git was a file --- when the new
XDG_CONFIG_HOME support looks for ~/.config/git/config it should
ignore ~/.config/git instead of printing irritating warnings:

 $ git status -s
 warning: unable to access '/home/jrn/.config/git/config': Not a directory
 warning: unable to access '/home/jrn/.config/git/config': Not a directory
 warning: unable to access '/home/jrn/.config/git/config': Not a directory
 warning: unable to access '/home/jrn/.config/git/config': Not a directory

Compare v1.7.12.1~2^2 (attr:failure to open a .gitattributes file
is OK with ENOTDIR, 2012-09-13).

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>