### Please describe the problem.
I just installed git-annex-20130601 on Gentoo and when running git annex webapp it started to run things on wine.

### What steps will reproduce the problem?
On Gentoo ~amd64:
[[!format sh """
 ~$ layman -a haskell
 ~$ USE=webapp emerge -1 git-annex
 ~$ git annex webapp
"""]]
### What version of git-annex are you using? On what operating system?
dev-vcs/git-annex-4.20130601 from https://github.com/gentoo-haskell/gentoo-haskell/tree/master/dev-vcs/git-annex

On Gentoo ~amd64

### 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
~$ git annex webapp
Launching web browser on file:///tmp/webapp14071.html
libpng warning: Application built with libpng-1.6.2 but running with 1.5.13
err:menubuilder:convert_to_native_icon error 0x80004005 initializing encoder
libpng warning: Application built with libpng-1.6.2 but running with 1.5.13
err:menubuilder:convert_to_native_icon error 0x80004005 initializing encoder
libpng warning: Application built with libpng-1.6.2 but running with 1.5.13
err:menubuilder:convert_to_native_icon error 0x80004005 initializing encoder
...
fixme:exec:SHELL_execute flags ignored: 0x00000100
fixme:exec:SHELL_execute flags ignored: 0x00000100
fixme:exec:SHELL_execute flags ignored: 0x00000100
...

22185 me     20   0 2580M 10196  8156 S  0.0  0.1  0:00.09 ├─ start /ProgIDOpen htmlfile /home/reinis/.wine/dosdevices/z:/tmp/webapp2554.html
 2597 me     21   1 2596M 10984  8764 S  0.0  0.1  0:01.23 ├─ c:\windows\system32\explorer.exe /desktop
 2589 me     20   0 2581M  2344  1932 S  0.0  0.0  0:00.00 ├─ c:\windows\system32\plugplay.exe
 2581 me     20   0 2593M  8900  7500 S  0.0  0.1  0:00.09 ├─ c:\windows\system32\winedevice.exe MountMgr
 2577 me     20   0 2583M  2776  2272 S  0.0  0.0  0:00.00 ├─ c:\windows\system32\services.exe
 2571 me     20   0 24960  7532   772 S 46.1  0.1  2:29.06 ├─ /usr/bin/wineserver

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

> [[done]]; this is a misconfigured system, not a git-annex bug, 
> and git-annex honors git config web.browser to allow working around
> this. --[[Joey]]