Changing the codes used in the C-x v d display

[Eric S. Raymond]

Dan wrote:
>BTW, for consistency with PCL-CVS and with the vc-dired display for
>other states shouldn't "(Unknown)" be better than just "?" ?

I went with "?" partly because I'm thinking that it might be a good idea 
to change the convention used for the status codes.  Specifically I think
we ought to look at following Subversion's practice, the way later
VCSes have tended to.  Look at this:

VC status        Subversion  Mercurial    Bazaar
---------------  ----------  ----------   ---------
up-to-date       (space)     [2]          (space)
edited           M           M            M
USER             USER[1]     [3]          [3]
needs-patch      *           [3]          [3]
needs-merge      C           [3]          [3]
unlocked-changes K,B         [3]          [3]
added            A           A            A
ignored          I           I            I
unregistered     ?           ?            ?

The bzr documentation says explicitly that its bzr status --short codes
are like Subversion's.  I got the Mercurial ones by looking at the
output of "hg help status".

[1] Only in -v mode

I added "unregistered" and "ignored" because it looks like we're going to 
have to add these states to ouur repertoire to further speed up dir-state.

[2] hg status does not list unmodified files

[3] No such status in this system, it has a commit-before-merge model.

The M, I, A and ? codes are consistent across all three of these systems and 
I'm thinking (a) that's by design, (b) it's a good idea, and (c) we 
should probably emulate it.  

When I originally wrote VC there were no standards for these flags, so
inventing our own was necessary.  But now that there is a de-facto standard
a VC-Dired display that follows it makes one less detail for VC users to
have to learn.
-- 
                <a href="http://www.catb.org/~esr/";>Eric S. Raymond</a>

"One of the ordinary modes, by which tyrants accomplish their purposes
without resistance, is, by disarming the people, and making it an
offense to keep arms."
        -- Constitutional scholar and Supreme Court Justice Joseph Story, 1840