phases: add a very simple test

Note that the expected output is wrong as is should be phase-1. But
the machinery to plant new root is to come in later commit.

tests/test-phases.t

@@ -0,0 +1,10 b''
+  $ alias hglog='hg log --template "{rev} {phase} {desc}\n"'
+
+  $ hg init initialrepo
+  $ cd initialrepo
+  $ touch sam
+  $ hg add sam
+  $ hg ci -m 'first'
+
+  $ hglog
+  0 0 first