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.

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adding foo

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Patch queue now empty

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applying patch1

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applying patch2

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applying bad-patch

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transaction abort!

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rollback completed

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cleaning up working directory...done

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abort: decoding near 'é': 'ascii' codec can't decode byte 0xe9 in position 0: ordinal not in range(128)!

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changeset:   0:bbd179dfa0a7

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tag:         tip

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user:        test

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date:        Thu Jan 01 00:00:00 1970 +0000

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summary:     add foo

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% bar should be gone; other unknown/ignored files should still be around

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? untracked-file

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I .hgignore

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C foo