amend: rectify comment
Comment was ambiguous as there can be two parents of a changeset in mercurial.
This commit fixes the comment to clarify that the first parent is being
considered.
Test Plan:
ran the test suite
Differential Revision: https://phab.mercurial-scm.org/D595
--- a/mercurial/cmdutil.py Fri Sep 01 15:08:54 2017 -0700
+++ b/mercurial/cmdutil.py Thu Aug 31 18:35:39 2017 -0700
@@ -3069,7 +3069,7 @@
# |
# old o - changeset to amend
# |
- # base o - parent of amending changeset
+ # base o - first parent of the changeset to amend
# Update extra dict from amended commit (e.g. to preserve graft
# source)