non-recursive path limits

Is there a way to perform non-recursive path limiting on functions  
like 'git log', 'git format-patch', etc.

Each of these functions can limit to a path using the '-- <path>'  
notation.  By default, it recursively
goes down the directory tree.  I would like to limit the tree descent  
to one level.  For example,

repos/a-dir/a1.c
repos/a-dir/a2.c
repos/a-dir/a-lib/alib1.c
repos/a-dir/a-lib/alib2.c

If we are in repos, then 'git log -- a-dir' will show all four files.   
However, I only wish to see the
output for all files that are the 'a-dir' level.  For the above, that  
would consist of a1.c and a2.c.
However, I also wish to see any files that might have existed in the  
history at this level.  I know
I can do 'git log -- a-dir/a1.c' to search all history for the a1.c  
file, but I want the history of the
a-dir directory (only).

Is there a way to accomplish this?

Thanks,

Paul