revsets: let p1() and p2() return parents of working dir

revsets: let p1() and p2() return parents of working dir

This patch makes the 'set' argument to revset functions p1() and p2()
optional. If no argument is given, p1() and p2() return the first or second
parent of the working directory.

If the working directory is not an in-progress merge (no 2nd parent), p2()
returns the empty set. For a checkout of the null changeset, both p1() and
p2() return the empty set.

--- a/mercurial/revset.py	Thu Nov 04 09:04:37 2010 +0100
+++ b/mercurial/revset.py	Thu Nov 04 16:59:03 2010 -0500
@@ -202,9 +202,12 @@
     return [r for r in subset if r == l]
 
 def p1(repo, subset, x):
-    """``p1(set)``
-    First parent of changesets in set.
+    """``p1([set])``
+    First parent of changesets in set, or the working directory.
     """
+    if x is None:
+        return [repo[x].parents()[0].rev()]
+
     ps = set()
     cl = repo.changelog
     for r in getset(repo, range(len(repo)), x):
@@ -212,9 +215,16 @@
     return [r for r in subset if r in ps]
 
 def p2(repo, subset, x):
-    """``p2(set)``
-    Second parent of changesets in set.
+    """``p2([set])``
+    Second parent of changesets in set, or the working directory.
     """
+    if x is None:
+        ps = repo[x].parents()
+        try:
+            return [ps[1].rev()]
+        except IndexError:
+            return []
+
     ps = set()
     cl = repo.changelog
     for r in getset(repo, range(len(repo)), x):

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/test-revset-dirstate-parents.t	Thu Nov 04 16:59:03 2010 -0500
@@ -0,0 +1,42 @@
+  $ HGENCODING=utf-8
+  $ export HGENCODING
+
+  $ try() {
+  >   hg debugrevspec --debug $@
+  > }
+
+  $ log() {
+  >   hg log --template '{rev}\n' -r "$1"
+  > }
+
+  $ hg init repo
+  $ cd repo
+
+  $ try 'p1()'
+  ('func', ('symbol', 'p1'), None)
+  -1
+  $ try 'p2()'
+  ('func', ('symbol', 'p2'), None)
+
+null revision
+  $ log 'p1()'
+  $ log 'p2()'
+
+working dir with a single parent
+  $ echo a > a
+  $ hg ci -Aqm0
+  $ log 'p1()'
+  0
+  $ log 'p2()'
+
+merge in progress
+  $ echo b > b
+  $ hg ci -Aqm1
+  $ hg up -q 0
+  $ echo c > c
+  $ hg ci -Aqm2
+  $ hg merge -q
+  $ log 'p1()'
+  2
+  $ log 'p2()'
+  1