Calling revlog.addgroup with an empty changegroup now raises RevlogError.
The empty changegroup can be caused by remote servers dying soon after
findincoming, and further code in pull assumes (correctly) that there are
new changesets.
adding foo
adding bar
adding baz/bletch
test-archive-TIP/bar
test-archive-TIP/baz/bletch
test-archive-TIP/foo
test-archive-TIP/bar
test-archive-TIP/baz/bletch
test-archive-TIP/foo
Archive: archive.zip
testing: test-archive-TIP/bar OK
testing: test-archive-TIP/baz/bletch OK
testing: test-archive-TIP/foo OK
No errors detected in compressed data of archive.zip.