Adding Exit status documentation to all git commands starting with git status

[nadim khemir <nadim@khemir.net>]

I was asking on the irc channel about how to know if I need to commit. I 
promptely got answered but during the discussion, the few of us still awake 
in the middle of the night (for me at least), agreed that it would be good to 
have a EXIT STATUS in all the commands documentation starting with 
the 'status' command.

The current documentation of 'git status' does cover exit status and looks 
like:
<original>
...
shows what would be committed if the same options are given to
'git-commit'.

If there is no path that is different between the index file and
the current HEAD commit (i.e., there is nothing to commit by running
`git commit`), the command exits with non-zero status.


OUTPUT
------
</original>

There are different styles to add exit status, give me your input on why and 
why not using one or the other. I list 3 solutions and what I think about 
them.

<solution 1, least change, easier to recognize although all the negations and 
the explaination being about when the command ~fails~ makes newbies head spin 
for a few seconds>

...
shows what would be committed if the same options are given to
'git-commit'.

EXIT STATUS
-----------
The command exits with non-zero status if there is no path that is 
different between the index file and the current HEAD commit (i.e.,
there is nothing to commit by running `git commit`).


OUTPUT
------
</solution 1>



<solution 2, both zero and non zero status>

...
shows what would be committed if the same options are given to
'git-commit'.

EXIT STATUS
-----------
Zero status:      There is a different between the index file and HEAD.
Non-zero status:  There is nothing to commit by running `git commit`. 


OUTPUT
------
</solution 2>



<solution 3, Only zero status, non zero is easilly deducted. Clearest IMO>

...
shows what would be committed if the same options are given to
'git-commit'.

EXIT STATUS
-----------
Zero status: There is a different between the index and HEAD; running 
`git commit` would create a new commit. 


OUTPUT
------
</solution 3>



A few things could be better explained:
	- The command is to be run with '-a' as option. 
	- The fact that non add'ed files are not taken into account is not
completely obvious. The first paragraph of the DESCRIPTION explains it but it  
is not the clearest explaination ever (maybe because it's not easy to explain 
and man pages are references not user manuals)

Cheers, Nadim.