scmutil: extract helper functions that returns human-readable change id
We do "'%d:%s' % (ctx...)" at several places, so let's formalize it. A low-
level function, formatrevnode(ui, rev, node), is extracted so we can pass
a manifest rev/node pair.
Note that hex() for manifest output can be replaced with hexfunc() because
it is printed only when debugflag is set.
i18n/de.po is updated so test-log.t passes with no error.
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ echo 'base' > base
$ hg ci -Ambase
adding base
$ hg qnew -mmqbase mqbase
$ hg qsave
$ hg qrestore 2
restoring status: hg patches saved state