unlike `hg log -r null:0`, which is a set of two revisions.

fixture:

  $ export HGRCPATH="$PWD/hgrc"
  $ cat > "$HGRCPATH" <<EOF
  > [ui]
  > interactive = False
  > logtemplate = "{ifeq(rev, '-1', '(init) ', '{desc|firstline|nonempty}')} {rev}\n"
  > quiet = True
  > username = J. Random Hacker <hackjr@example.org>
  > [extensions]
  > hgext.graphlog =
  > EOF

  $ hg init
  $ for i in 0 1 2; do
  >   echo c$i > f
  >   hg ci -Am commit-$i f
  > done

  $ hg glog -r tip:null
  @  commit-2 2
  |
  o  commit-1 1
  |
  o  commit-0 0
  |
  o  (init)  -1


one of these is unlike the others:

  $ hg log -r null:null
  (init)  -1

  $ hg log -r null:null
  (init)  -1

  $ hg log -r null:0
  (init)  -1
  commit-0 0

  $ hg log -r 0:null
  (init)  -1

  $ hg log -r null:1
  (init)  -1
  commit-0 0
  commit-1 1

  $ hg log -r 1:null
  commit-1 1
  commit-0 0
  (init)  -1

  $ hg log -r null:2
  (init)  -1
  commit-0 0
  commit-1 1
  commit-2 2

  $ hg log -r 2:null
  commit-2 2
  commit-1 1
  commit-0 0
  (init)  -1