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 "imerge=" >> $HGRCPATH
HGMERGE=true
export HGMERGE
hg init base
cd base
echo foo > foo
echo bar > bar
hg ci -Am0 -d '0 0'
hg mv foo foo2
echo foo >> foo2
hg ci -m1 -d '1 0'
hg up -C 0
echo bar >> foo
echo bar >> bar
hg ci -m2 -d '2 0'
echo % start imerge
hg imerge
cat foo2
cat bar
echo % status -v
hg -v imerge st
echo % next
hg imerge next
echo % merge next
hg --traceback imerge
echo % unresolve
hg imerge unres foo
echo % merge foo
hg imerge merge foo
echo % save
echo foo > foo2
hg imerge save ../savedmerge
echo % load
hg up -C 0
hg imerge --traceback load ../savedmerge
cat foo2
hg ci -m'merged' -d '3 0'
hg tip -v
echo % nothing to merge -- tip
hg imerge
hg up 0
echo % nothing to merge
hg imerge
exit 0