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 a
cd a
echo a > foo
hg rm foo
hg add foo
hg commit -m 1 -d "1000000 0"
hg remove
rm foo
hg remove foo
hg revert --all
rm foo
hg remove --after
hg commit -m 2 -d "1000000 0"
hg export --nodates 0
hg export --nodates 1
hg log -p -r 0
hg log -p -r 1
echo a > a
hg add a
hg rm a
hg rm -f a
echo b > b
mkdir c
echo d > c/d
hg ci -A -m 3 -d "1000001 0"
echo c >> b
hg rm b
hg rm -f b
hg rm -A c/d
hg st
cat c/d
hg revert c
hg rm -A
hg st
hg rm -A c
hg st
rm c/d
hg rm -A
hg st
cd ..
hg clone a b