Re: Clean up sha1 file writing

Linus Torvalds [off-list ref] writes:

... On the other hand, from a longer-term 
maintenance standpoint and from a "be much more careful when doing file 
writes" standpoint, I think it's worth it.

The re-write is "obviously correct" (famous last words) and is mostly 
just moving code around and getting rid of a few temporaries that become 
unnecessary as a result.

The patch looks a bit messy: the changes aren't actually that big, but the 
split-up and the resulting re-indentation makes the patch fairly 
unreadable, so the cleanups are more obvious when you look at the 
before-and-after side by side rather than when looking at the unified 
diff..)

I usually work in text-only terminal, but with the above
warning, I did this:

	git cat-file -p HEAD^:sha1_file.c >/var/tmp/1
        xxdiff /var/tmp/1 sha1_file.c
        
with ignorespace and stuff enabled.  It was very pleasant to
read the changes that way, especially around write_sha1_to_fd()
vs repack_object().  xxdiff is my new friend.