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
# test that we don't interrupt the merge session if
# a file-level merge failed
hg init repo
cd repo
echo foo > foo
echo a > bar
hg ci -Am 'add foo' -d '0 0'
hg mv foo baz
echo b >> bar
echo quux > quux1
hg ci -Am 'mv foo baz' -d '0 0'
hg up -qC 0
echo >> foo
echo c >> bar
echo quux > quux2
hg ci -Am 'change foo' -d '0 0'
# test with the rename on the remote side
HGMERGE=false hg merge
# test with the rename on the local side
hg up -C 1
HGMERGE=false hg merge
true