### Please describe the problem.

spotted that in my script I have "incorrectly" passed both -c and its value within the same single argument ('-c annex....').  But surprisingly annex neither treated it correctly, nor complained that something was incorrectly passed in.  Shouldn't it fail if option is not '-c' but '-c smthelse' or correctly treat the value in such as case?

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

5.20151104+gitge9cdce6-1~ndall+1

### Please provide any additional information below.

[[!format sh """
$> ls -ld svgtune-0.2.0/README.rst
-rw------- 1 yoh yoh 9 Nov 12 12:03 svgtune-0.2.0/README.rst

$> git-annex add --debug '-c annex.largefiles=exclude=*.rst' svgtune-0.2.0/README.rst 
add svgtune-0.2.0/README.rst ok
(recording state in git...)

$> ls -ld svgtune-0.2.0/README.rst                                                   
lrwxrwxrwx 1 yoh yoh 189 Nov 12 12:03 svgtune-0.2.0/README.rst -> ../.git/annex/objects/32/vx/SHA256E-s9--246c960678ee9a80aa6d2eff2f1df1debd590cb73aa5fed6cb4b13b8018599f5.rst/SHA256E-s9--246c960678ee9a80aa6d2eff2f1df1debd590cb73aa5fed6cb4b13b8018599f5.rst
"""]]

[[!meta author=yoh]]

> I guess it could be considered [[done]] --[[yoh]]