convert: document parent order in splicemap help (issue1764)

hgext/convert/__init__.py

@@ -103,7 +103,10 b' def convert(ui, src, dest=None, revmapfi'
     revision control system whose parents should be modified (same
     format as a key in .hg/shamap). The values are the revision IDs
     (in either the source or destination revision control system) that
-    should be used as the new parents for that node.
+    should be used as the new parents for that node. For example, if
+    you have merged "release-1.0" into "trunk", then you should
+    specify the revision on "trunk" as the first parent and the one on
+    the "release-1.0" branch as the second.
 
     The branchmap is a file that allows you to rename a branch when it is
     being brought in from whatever external repository. When used in

tests/test-convert.out

@@ -81,7 +81,10 b' convert a foreign SCM repository to a Me'
     revision ID in the source revision control system whose parents should be
     modified (same format as a key in .hg/shamap). The values are the revision
     IDs (in either the source or destination revision control system) that
-    should be used as the new parents for that node.
+    should be used as the new parents for that node. For example, if you have
+    merged "release-1.0" into "trunk", then you should specify the revision on
+    "trunk" as the first parent and the one on the "release-1.0" branch as the
+    second.
 
     The branchmap is a file that allows you to rename a branch when it is
     being brought in from whatever external repository. When used in