archive: use util.opener when archiving files.
This simplifies the code a bit and makes it easier to support symlinks.
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