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.
pulling from source1
requesting all changes
adding changesets
adding manifests
adding file changes
added 10 changesets with 10 changes to 1 files
(run 'hg update' to get a working copy)
requesting all changes
adding changesets
adding manifests
adding file changes
added 10 changesets with 10 changes to 1 files
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 10 changesets, 10 total revisions
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 10 changesets, 10 total revisions