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

cat <<EOF > merge
import sys, os
print "merging for", os.path.basename(sys.argv[1])
EOF
HGMERGE="python ../merge"; export HGMERGE

mkdir A1
cd A1
hg init
echo This is file foo1 > foo
echo This is file bar1 > bar
hg add foo bar
hg commit -m "commit text" -d "1000000 0"

cd ..
hg clone A1 B1

cd A1
rm bar
hg remove bar
hg commit -m "commit test" -d "1000000 0"

cd ../B1
echo This is file foo22 > foo
hg commit -m "commit test" -d "1000000 0"

cd ..
hg clone A1 A2
hg clone B1 B2

cd A1
hg pull ../B1
hg merge
hg commit -m "commit test" -d "1000000 0"
echo bar should remain deleted.
hg manifest --debug

cd ../B2
hg pull ../A2
hg merge
hg commit -m "commit test" -d "1000000 0"
echo bar should remain deleted.
hg manifest --debug