Fix accidentally broken test.

Merge with crew.

Allow tests to run in parallel.

run-tests.py: reorder options alphabetically.

convert_svn: add --filemap support

convert_cvs: add --filemap support

convert_git: add --filemap support

mercurial_source: add --filemap support

convert: add a mode where mercurial_sink skips empty revisions. The getchanges function of some converter_source classes can return some false positives. I.e. they sometimes claim that a file "foo" was changed in some revision, even though its contents are still the same. convert_svn is particularly bad, but I think this can also happen with convert_cvs and, at least in theory, with mercurial_source. For regular conversions this is not really a problem - as long as getfile returns the right contents, we'll get a converted revision with the right contents. But when we use --filemap, this could lead to superfluous revisions being converted. Instead of fixing every converter_source, I decided to change mercurial_sink to work around this problem. When --filemap is used, we're interested only in revisions that touch some specific files. If a revision doesn't change any of these files, then we're not interested in it (at least for revisions with a single parent; merges are special). For mercurial_sink, we abuse this property and rollback a commit if the manifest text hasn't changed. This avoids duplicating the logic from localrepo.filecommit to detect unchanged files.

convert: readd --filemap To handle merges correctly, this revision adds a filemap_source class that wraps a converter_source and does the work necessary to calculate the subgraph we're interested in. The wrapped converter_source must provide a new getchangedfiles method that, given a revision rev, and an index N, returns the list of files that are different in rev and its Nth parent. The implementation depends on the ability to skip some revisions and to change the parents field of the commit objects that we returned earlier. To make the conversion restartable, we assume the revisons in the revmapfile are topologically sorted.