revset: added lazyset implementation to desc revset
Performance benchmarking:
$ time hg log -qr "first(desc(hg))"
changeset: 0:
9117c6561b0b
real 0m2.210s
user 0m2.158s
sys 0m0.049s
$ time ./hg log -qr "first(desc(hg))"
changeset: 0:
9117c6561b0b
real 0m0.171s
user 0m0.131s
sys 0m0.035s
$ hg init
$ touch a
$ hg add a
$ hg ci -m "a"
$ echo 123 > b
$ hg add b
$ hg diff --nodates
diff -r 3903775176ed b
--- /dev/null
+++ b/b
@@ -0,0 +1,1 @@
+123
$ hg diff --nodates -r tip
diff -r 3903775176ed b
--- /dev/null
+++ b/b
@@ -0,0 +1,1 @@
+123
$ echo foo > a
$ hg diff --nodates
diff -r 3903775176ed a
--- a/a
+++ b/a
@@ -0,0 +1,1 @@
+foo
diff -r 3903775176ed b
--- /dev/null
+++ b/b
@@ -0,0 +1,1 @@
+123
$ hg diff -r ""
hg: parse error: empty query
[255]
$ hg diff -r tip -r ""
hg: parse error: empty query
[255]