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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#!/bin/sh

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hg --debug init

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echo this is a1 > a

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hg add a

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hg commit -m0 -d "1000000 0"

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echo this is b1 > b

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hg add b

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hg commit -m1 -d "1000000 0"

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hg manifest --debug 1

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echo this is c1 > c

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hg rawcommit -p 1 -d "1000000 0" -m2 c

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hg manifest --debug 2

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hg -v parents

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rm b

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hg rawcommit -p 2 -d "1000000 0" -m3 b

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hg manifest --debug 3

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hg -v parents

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echo this is a22 > a

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hg rawcommit -p 3 -d "1000000 0" -m4 a

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hg manifest --debug 4

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hg -v parents

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echo this is c22 > c

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hg rawcommit -p 1 -d "1000000 0" -m5 c

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hg manifest --debug 5

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hg -v parents

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# merge, but no files changed

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hg rawcommit -p 4 -p 5 -d "1000000 0" -m6

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hg manifest --debug 6

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hg -v parents

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# no changes what-so-ever

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hg rawcommit -p 6 -d "1000000 0" -m7

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hg manifest --debug 7

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hg -v parents