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.

#!/bin/sh

echo "[extensions]" >> $HGRCPATH
echo "hgext.convert=" >> $HGRCPATH

hg init orig
cd orig

echo foo > foo
echo bar > bar
hg ci -qAm 'add foo bar' -d '0 0'

echo >> foo
hg ci -m 'change foo' -d '1 0'

hg up -qC 0
hg copy --after --force foo bar
hg copy foo baz
hg ci -m 'make bar and baz copies of foo' -d '2 0'

hg merge
hg ci -m 'merge local copy' -d '3 0'

hg up -C 1
hg merge 2
hg ci -m 'merge remote copy' -d '4 0'

cd ..
hg convert --datesort orig new 2>&1 | grep -v 'subversion python bindings could not be loaded'
cd new
hg out ../orig

true