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 and bar' -d '0 0'

hg rm foo
hg ci -m 'remove foo' -d '0 0'

mkdir foo
echo file > foo/file
hg ci -qAm 'add foo/file' -d '0 0'

hg tag -d '0 0' some-tag

hg log
cd ..

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

echo '% dirstate should be empty:'
hg debugstate
hg parents -q

hg up -C
hg copy bar baz
echo '% put something in the dirstate:'
hg debugstate > debugstate
grep baz debugstate

echo '% add a new revision in the original repo'
cd ../orig
echo baz > baz
hg ci -qAm 'add baz'

cd ..
hg convert orig new 2>&1 | grep -v 'subversion python bindings could not be loaded'
cd new
hg out ../orig
echo '% dirstate should be the same (no output below):'
hg debugstate > new-debugstate
diff debugstate new-debugstate

echo '% no copies'
hg up -C
hg debugrename baz