cabal no longer supports package version tags

(Imported from [Trac #900](http://hackage.haskell.org/trac/hackage/ticket/900), reported by guest on 2011-11-20)

The following cabal file below triggers an assertion fail on the second install:

$ cabal --version

cabal-install version 0.13.3

using version 1.13.3 of the Cabal library

$ cabal install

Resolving dependencies...

Configuring foobar-0.2.0...

Building foobar-0.2.0...

Preprocessing library foobar-0.2.0...

[1 of 1] Compiling FooBar           ( FooBar.hs, dist/build/FooBar.o )

[1 of 1] Compiling FooBar           ( FooBar.hs, dist/build/FooBar.p_o )

Registering foobar-0.2.0...

Installing library in /home/hvr/.cabal/lib/foobar-0.2.0/ghc-7.2.2

Registering foobar-0.2.0...

$ cabal install

Resolving dependencies...

Configuring foobar-0.2.0...

cabal: Distribution/Simple/PackageIndex.hs:123:8-13: Assertion failed

Only when I unregister the installed package via ghc-pkg unregister foobar I can configure the package again...

The cabal file causing this behaviour:

name:                foobar

version:             0.2.0-git20111120

synopsis:            none

license:             BSD3

license-file:        LICENSE

author:              foo

maintainer:          foo@bar

build-type:          Simple

cabal-version:       >=1.10

library

  default-language: Haskell2010

  exposed-modules: FooBar

  build-depends: base

The FooBar module is just a dummy empty module. This used to work previously, e.g. with

$ cabal-0.11.2  --version

cabal-install version 0.11.2

using version 1.12.0 of the Cabal library