ui: add diff.showfunc to tweakdefaults
This is a little risky, as I think we can have some encoding weirdness
crop up. showfunc also isn't the most robust feature, but it's still
often useful context...
Differential Revision: https://phab.mercurial-scm.org/D1610
#require serve killdaemons
$ hg clone http://localhost:$HGPORT/ copy
abort: * (glob)
[255]
$ test -d copy
[1]
$ $PYTHON "$TESTDIR/dumbhttp.py" -p $HGPORT --pid dumb.pid
$ cat dumb.pid >> $DAEMON_PIDS
$ hg clone http://localhost:$HGPORT/foo copy2
abort: HTTP Error 404: * (glob)
[255]
$ killdaemons.py