util._matcher: speed up regexp matching.
In 4babaa52badf, Benoit made a change that substantially slows matching
when a big .hgignore file is in play, because it calls into the regexp
matching engine potentially hundreds of times per file to be matched.
I've partly rolled back his change, so that we only call into the matcher
once per file, but preserved the ability to report a meaningful error
message if there's a syntax error in the regexp.
#!/bin/sh -e
umask 027
mkdir test1
cd test1
hg init
touch a b
hg add a b
hg ci -m "added a b" -d "1000000 0"
cd ..
hg clone test1 test3
mkdir test2
cd test2
hg init
hg pull ../test1
hg co
chmod +x a
hg ci -m "chmod +x a" -d "1000000 0"
cd ../test1
echo 123 >>a
hg ci -m "a updated" -d "1000000 0"
hg pull ../test2
hg heads
hg history
hg -v merge
cd ../test3
echo 123 >>b
hg ci -m "b updated" -d "1000000 0"
hg pull ../test2
hg heads
hg history
hg -v merge
ls -l ../test[123]/a > foo
cut -b 1-10 < foo
hg debugindex .hg/store/data/a.i
hg debugindex ../test2/.hg/store/data/a.i
hg debugindex ../test1/.hg/store/data/a.i