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 -e

umask 027
mkdir test1
cd test1

hg init
touch a b
hg add a b
hg ci -m "added a b" -d "1000000 0"

cd ..
hg clone test1 test3
mkdir test2
cd test2

hg init
hg pull ../test1
hg co
chmod +x a
hg ci -m "chmod +x a" -d "1000000 0"
echo % the changelog should mention file a:
hg tip --template '#files#\n'

cd ../test1
echo 123 >>a
hg ci -m "a updated" -d "1000000 0"

hg pull ../test2
hg heads
hg history

hg -v merge

cd ../test3
echo 123 >>b
hg ci -m "b updated" -d "1000000 0"

hg pull ../test2
hg heads
hg history

hg -v merge

ls -l ../test[123]/a > foo
cut -b 1-10 < foo

hg debugindex .hg/store/data/a.i
hg debugindex ../test2/.hg/store/data/a.i
hg debugindex ../test1/.hg/store/data/a.i