revset: optimize missing ancestor expressions
A missing ancestor expression is any expression of the form (::x - ::y) or
equivalent. Such expressions are remarkably common, and so far have involved
multiple walks down the DAG, followed by a set difference operation.
With this patch, such expressions will be transformed into uses of the fast
algorithm at ancestor.missingancestor.
For a repository with over 600,000 revisions, perfrevset for '::tip - ::-10000'
returns:
Before: ! wall 3.999575 comb 4.000000 user 3.910000 sys 0.090000 (best of 3)
After: ! wall 0.132423 comb 0.130000 user 0.130000 sys 0.000000 (best of 75)
basic test for hg debugrebuildstate
$ hg init repo
$ cd repo
$ touch foo bar
$ hg ci -Am 'add foo bar'
adding bar
adding foo
$ touch baz
$ hg add baz
$ hg rm bar
$ hg debugrebuildstate
state dump after
$ hg debugstate --nodates | sort
n 644 -1 bar
n 644 -1 foo
status
$ hg st -A
! bar
? baz
C foo
$ cd ..