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
*** 'a\nc\n\n\n\n' 'a\nb\n\n\n'
*** 'a\nb\nc\n' 'a\nc\n'
*** '' ''
*** 'a\nb\nc' 'a\nb\nc'
*** 'a\nb\nc\nd\n' 'a\nd\n'
*** 'a\nb\nc\nd\n' 'a\nc\ne\n'
*** 'a\nb\nc\n' 'a\nc\n'
*** 'a\n' 'c\na\nb\n'
*** 'a\n' ''
*** 'a\n' 'b\nc\n'
*** 'a\n' 'c\na\n'
*** '' 'adjfkjdjksdhfksj'
*** '' 'ab'
*** '' 'abc'
*** 'a' 'a'
*** 'ab' 'ab'
*** 'abc' 'abc'
*** 'a\n' 'a\n'
*** 'a\nb' 'a\nb'
6 6 'y\n\n'
6 6 'y\n\n'
9 9 'y\n\n'
done
done