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

"$TESTDIR/hghave" symlink || exit 80

origdir=`pwd`

cat >> readlink.py <<EOF
import os
import sys

for f in sys.argv[1:]:
    print f, '->', os.readlink(f)
EOF

hg init repo
cd repo
ln -s nothing dangling
hg ci -qAm 'add symlink'

hg archive -t files ../archive
hg archive -t tar -p tar ../archive.tar
hg archive -t zip -p zip ../archive.zip

echo '% files'
cd "$origdir"
cd archive
python ../readlink.py dangling

echo '% tar'
cd "$origdir"
tar xf archive.tar
cd tar
python ../readlink.py dangling

echo '% zip'
cd "$origdir"
unzip archive.zip > /dev/null
cd zip
python ../readlink.py dangling