Commit Briefs
use fd instead of pid for tx locking
c->iev.ibuf.pid is our pid, not sure why, but fd is just as well as easier to use.
print the "> " prefix only if -p is given
the prefix is nice to see, but can break the amused show | filters ... | amused load because sort(1), uniq(1) etc don't know how to strip the "> " and " " prefixes obviously.
rewrite `load' to use the new transaction messages
this allows to do stuff like amused show | some shell filtering | amused load without the dangers of races between show and load.