You're also correct about hg not versioning empty directories with the default mercurial install. A previous place I worked had a non-standard extension - that

You're also correct about hg not versioning empty directories with the default mercurial install. A previous place I worked had a non-standard extension - that unknown to me may very well have used the .keep file trick you described. So it would appear that fossil not supporting versioning of directories puts it in good SCM company.