log: document the characters ---graph uses to draw
The meaning of : vs | was undocumented and non-obvious.
--- a/mercurial/commands.py Tue Apr 25 00:19:03 2017 -0700
+++ b/mercurial/commands.py Tue Apr 18 14:51:32 2017 -0700
@@ -3334,6 +3334,8 @@
'o' is a changeset, '@' is a working directory parent, 'x' is obsolete,
and '+' represents a fork where the changeset from the lines below is a
parent of the 'o' merge on the same line.
+ Paths in the DAG are represented with '|', '/' and so forth. ':' in place
+ of a '|' indicates one or more revisions in a path are omitted.
.. note::