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)
$ hg init
$ touch a
$ unset HGUSER
$ echo "[ui]" >> .hg/hgrc
$ echo "username= foo" >> .hg/hgrc
$ echo " bar1" >> .hg/hgrc
$ hg ci -Am m
adding a
abort: username 'foo\nbar1' contains a newline
[255]
$ rm .hg/hgrc
$ HGUSER=`(echo foo; echo bar2)` hg ci -Am m
abort: username 'foo\nbar2' contains a newline
[255]
$ hg ci -Am m -u "`(echo foo; echo bar3)`"
transaction abort!
rollback completed
abort: username 'foo\nbar3' contains a newline!
[255]