Why do I get “abort: requirement fncache not supported!” when invoking hg?
In version 1.1 of a new repository format was introduced to work around file name limitations on Windows. Repositories created with Mercurial 1.1 or later will automatically have enabled the fncache repository format. You need Mercurial 1.1 or later to read these repositories. Repositories created with pre 1.1 Mercurial or with fncache disabled can still be read. See the page about the fncache repository format for more information.