tests/test-merge-force.out

graphlog: split the actual DAG grapher out into a separate method

This allows extensions like pbranch to use asciigraph() to graph dependencies
for patch branches, but could be used for basically any DAG.

created new head
% local deleted a file, remote removed
abort: outstanding uncommitted changes
resolving manifests
removing a
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
(branch merge, don't forget to commit)
% should show a as removed
R a
% manifest. should not have a:
b