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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% create cvs repository

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% create source directory

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% import source directory

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N src/a

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N src/b/c

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No conflicts created by this import

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% checkout source directory

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U src/a

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U src/b/c

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% convert fresh repo

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initializing destination src-hg repository

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connecting to cvsrepo

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scanning source...

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sorting...

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converting...

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1 Initial revision

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0 import

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updating tags

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a

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c

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% commit new file revisions

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checking in src/a,v

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checking in src/b/c,v

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% convert again

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destination src-hg is a Mercurial repository

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connecting to cvsrepo

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scanning source...

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sorting...

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converting...

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0 ci1

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updating tags

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a

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a

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c

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c