### Please describe the problem.

[[!meta title="Empty files make git status slow in v6 repo"]]

When empty files are committed to a repository, git status becomes slow because git annex smudge is run for every empty file under git annex even with clean HEAD. I know git annex is for large files (rather than infinity small ones), but I'm using it to manage a GRASS GIS database, which oddly uses empty files for some things:/

### What steps will reproduce the problem?
```
# slow
touch emptyfile
git add emptyfile
git commit -a -m 'Added empty file.'
GIT_TRACE=1 git status

# fast
cat 1 > emptyfile
git commit -a -m 'Added a 1 to emptyfile.'
GIT_TRACE=1 git status
```

### What version of git-annex are you using? On what operating system?
- git-annex version: 6.20170228-g7a32e08c4
- operating system: linux x86_64 (SLE 12.2)
- local repository version: 6


### 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)
Yes, git with git annex has revolutionised my scientific project file organisation and thats why I want to improve it.
