obsolete: skip 'changectx' usage in unstable computation
We simplify the unstable computation code, skipping the expensive creation of
changectx object. We focus on efficient set operation and revnumber centric
functions.
In my mercurial development repository, this provides a 3x speedup to the
function:
before: 5.319 ms
after: 1.844 ms
repo details:
total changesets: 40886
obsolete changesets: 7756
mutable (not obsolete): 293
unstable: 30
$ hg init
$ $PYTHON -c 'file("a", "wb").write("confuse str.splitlines\nembedded\rnewline\n")'
$ hg ci -Ama -d '1 0'
adding a
$ echo clean diff >> a
$ hg ci -mb -d '2 0'
$ hg diff -r0 -r1
diff -r 107ba6f817b5 -r 310ce7989cdc a
--- a/a Thu Jan 01 00:00:01 1970 +0000
+++ b/a Thu Jan 01 00:00:02 1970 +0000
@@ -1,2 +1,3 @@
confuse str.splitlines
embedded\r (no-eol) (esc)
newline
+clean diff