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
unset HGUSER
EMAIL="My Name <myname@example.com>"
export EMAIL
hg init test
cd test
touch asdf
hg add asdf
hg commit -d '1000000 0' -m commit-1
hg tip
unset EMAIL
echo 1234 > asdf
hg commit -d '1000000 0' -u "foo@bar.com" -m commit-1
hg tip
echo "[ui]" >> .hg/hgrc
echo "username = foobar <foo@bar.com>" >> .hg/hgrc
echo 12 > asdf
hg commit -d '1000000 0' -m commit-1
hg tip
echo 1 > asdf
hg commit -d '1000000 0' -u "foo@bar.com" -m commit-1
hg tip
echo 123 > asdf
echo "[ui]" > .hg/hgrc
echo "username = " >> .hg/hgrc
hg commit -d '1000000 0' -m commit-1
rm .hg/hgrc
hg commit -d '1000000 0' -m commit-1 2>&1 | sed -e "s/'[^']*'/user@host/"