diff tests/test-revset.t @ 32699:f75d0aa5dc83

revset: lookup descendents for negative arguments to ancestor operator

Negative offsets to the `~` operator now search for descendents. The search is
aborted when a node has more than one child as we do not have a definition for
'nth child'. Optionally we can introduce such a notion and take the nth child
ordered by rev number.

The current revset language does provides a short operator for ancestor lookup
but not for descendents. This gives user a simple revset to move to the previous
changeset, e.g. `hg up '.~1'` but not to the 'next' changeset. With this change
userse can now use `.~-1` as a shortcut to move to the next changeset.
This fits better into allowing users to specify revisions via revsets and
avoiding the need for special `hg next` and `hg prev` operations.

The alternative to negative offsets is adding a new operator. We do not have
many operators in ascii left that do not require bash escaping (',', '_', and
'/' come to mind). If we decide that we should add a more convenient short
operator such as ('/', e.g. './1') we can later add it and allow ascendents
lookup via negative numbers.

--- a/tests/test-revset.t	Tue Jun 06 22:17:39 2017 +0530
+++ b/tests/test-revset.t	Sat May 27 10:25:09 2017 -0700
@@ -2975,6 +2975,14 @@
   $ log 'merge()^^^'
   1
 
+  $ log '(merge() | 0)~-1'
+  7
+  1
+  $ log 'merge()~-1'
+  7
+  $ log 'tip~-1'
+  $ log '(tip | merge())~-1'
+  7
   $ log 'merge()~0'
   6
   $ log 'merge()~1'
@@ -2995,6 +3003,10 @@
   hg: parse error: ^ expects a number 0, 1, or 2
   [255]
 
+  $ log 'branchpoint()~-1'
+  abort: revision in set has more than one child!
+  [255]
+
 Bogus function gets suggestions
   $ log 'add()'
   hg: parse error: unknown identifier: add