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

hg init test
cd test
cat >>afile <<EOF
0
EOF
hg add afile
hg commit -m "0.0"
cat >>afile <<EOF
1
EOF
hg commit -m "0.1"
cat >>afile <<EOF
2
EOF
hg commit -m "0.2"
cat >>afile <<EOF
3
EOF
hg commit -m "0.3"
hg update -C 0
cat >>afile <<EOF
1
EOF
hg commit -m "1.1"
cat >>afile <<EOF
2
EOF
hg commit -m "1.2"
cat >fred <<EOF
a line
EOF
cat >>afile <<EOF
3
EOF
hg add fred
hg commit -m "1.3"
hg mv afile adifferentfile
hg commit -m "1.3m"
hg update -C 3
hg mv afile anotherfile
hg commit -m "0.3m"
hg debugindex .hg/store/data/afile.i
hg debugindex .hg/store/data/adifferentfile.i
hg debugindex .hg/store/data/anotherfile.i
hg debugindex .hg/store/data/fred.i
hg debugindex .hg/store/00manifest.i
hg verify
cd ..
for i in 0 1 2 3 4 5 6 7 8; do
   hg clone -r "$i" test test-"$i"
   cd test-"$i"
   hg verify
   cd ..
done
cd test-8
hg pull ../test-7
hg verify