### Please describe the problem.
annex.largefiles saved in .gitattributes does not work when running 'git annex add' from a subdirectory

I set annex.largefiles to include any files larger than 50k or any files that are executable. This works if I'm adding a files from top level directory. But if I'm adding files from a sub-directory it does not work.

### What steps will reproduce the problem?
see log below

### What version of git-annex are you using? On what operating system?
ubuntu 15.10

git-annex version: 6.20160318-gd594fc0
build flags: Assistant Webapp Pairing Testsuite S3(multipartupload)(storageclasses) WebDAV Inotify DBus DesktopNotify XMPP ConcurrentOutput TorrentParser MagicMime Feeds Quvi
key/value backends: SHA256E SHA256 SHA512E SHA512 SHA224E SHA224 SHA384E SHA384 SHA3_256E SHA3_256 SHA3_512E SHA3_512 SHA3_224E SHA3_224 SHA3_384E SHA3_384 SKEIN256E SKEIN256 SKEIN512E SKEIN512 SHA1E SHA1 MD5E MD5 WORM URL
remote types: git gcrypt S3 bup directory rsync web bittorrent webdav tahoe glacier ddar hook external


### Please provide any additional information below.

[[!format sh """
# If you can, paste a complete transcript of the problem occurring here.
# If the problem is with the git-annex assistant, paste in .git/annex/daemon.log

vagrant@u240:/tmp/annex/$ git init
Initialized empty Git repository in /tmp/annex/.git/
vagrant@u240:/tmp/annex/$ git annex init
init  ok
(recording state in git...)
vagrant@u240:/tmp/annex/$ mkdir sub-dir
vagrant@u240:/tmp/annex/$ cp /bin/tempfile .
‘/bin/tempfile’ -> ‘./tempfile’
vagrant@u240:/tmp/annex/$ cp /bin/tempfile sub-dir/
‘/bin/tempfile’ -> ‘sub-dir/tempfile’
vagrant@u240:/tmp/annex/$ file --mime-type tempfile 
tempfile: application/x-executable
vagrant@u240:/tmp/annex/$ cat .gitattributes 
* annex.largefiles=((largerthan=50kb)or(mimetype=application/x-executable))
vagrant@u240:/tmp/annex/$ ls -l tempfile
-rwxr-xr-x 1 vagrant vagrant 10352 Apr  6 15:19 tempfile
# the file is 10k in size and I can annex it from top level directory
vagrant@u240:/tmp/annex/$ git annex add tempfile sub-dir/tempfile
add tempfile ok
add sub-dir/tempfile ok
(recording state in git...)
vagrant@u240:/tmp/annex/$ cp /bin/tempfile tempfile2
‘/bin/tempfile’ -> ‘tempfile2’
vagrant@u240:/tmp/annex/$ cp /bin/tempfile sub-dir/tempfile2
‘/bin/tempfile’ -> ‘sub-dir/tempfile2’
vagrant@u240:/tmp/annex/$ cd sub-dir/
# same file but I can not annex it if running from a sub-directory
vagrant@u240:/tmp/annex/sub-dir/$ git annex add ../tempfile2 tempfile2
add ../tempfile2 ok
add tempfile2 (non-large file; adding content to git repository) ok
(recording state in git...)
vagrant@u240:/tmp/annex/sub-dir/$ cd ..
vagrant@u240:/tmp/annex/$ ls -lR
.:
total 12
drwxrwxr-x 2 vagrant vagrant 4096 Apr  6 15:21 sub-dir/
lrwxrwxrwx 1 vagrant vagrant  186 Apr  6 15:19 tempfile -> .git/annex/objects/xj/kJ/SHA256E-s10352--93a1f74ec1714ef2107989076140b4eaae220f7b2cde834c16a7ad654d12b0f5/SHA256E-s10352--93a1f74ec1714ef2107989076140b4eaae220f7b2cde834c16a7ad654d12b0f5
lrwxrwxrwx 1 vagrant vagrant  186 Apr  6 15:20 tempfile2 -> .git/annex/objects/xj/kJ/SHA256E-s10352--93a1f74ec1714ef2107989076140b4eaae220f7b2cde834c16a7ad654d12b0f5/SHA256E-s10352--93a1f74ec1714ef2107989076140b4eaae220f7b2cde834c16a7ad654d12b0f5

./sub-dir:
total 16
lrwxrwxrwx 1 vagrant vagrant   189 Apr  6 15:20 tempfile -> ../.git/annex/objects/xj/kJ/SHA256E-s10352--93a1f74ec1714ef2107989076140b4eaae220f7b2cde834c16a7ad654d12b0f5/SHA256E-s10352--93a1f74ec1714ef2107989076140b4eaae220f7b2cde834c16a7ad654d12b0f5
-rwxr-xr-x 1 vagrant vagrant 10352 Apr  6 15:21 tempfile2


# End of transcript or log.
"""]]

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)


> Thanks for reporting. This was a dumb bug; it used the wrong path to the
> file for mimetype=, which was relative to the top of the repository.
> [[fixed|done]] --[[Joey]]
