preview of "What's cooking" (topics)

My git day this week hasn't started yet, but for people to base
their improvements on, here is a quick status before I go to
bed.

 - Detached HEAD along with two patches to teach git-status and
   git-branch about not being on any branch are in 'pu'; I
   removed -d option from git-checkout from the previous round.

 - Jürgen's git-status improvements are mostly in 'next' but
   one of them is queued in 'pu', waiting for comments.

 - I've queued my counterproposal to Shawn's lockfile fix in
   'pu', waiting for comments.

On the 'master' front, I've merged Andy's xwrite() loop.  I
think this is applicable to many other places after generalizing
it a bit more and perhaps merging it with safe_write in
pkt-line.c.

builtin-apply.c, builtin-unpack-objects.c, copy.c, csum-file.c,
index-pack.c, merge-recursive.c and pkt-line.c have
implementations of something very similar, with different policy
on error handling.

Also index-pack.c and upload-pack.c (in the status reporting
code path) also has unprotected xwrite() that can result in
short write.

Have fun.