Hi. Unfortunately:
$ debcheckout bustle
declared git repository at git://anonscm.debian.org/pkg-haskell/bustle.git
git clone git://anonscm.debian.org/pkg-haskell/bustle.git bustle ...
fatal: destination path 'bustle' already exists and is not an empty directory.
checkout failed (the command above returned a non-zero exit code)
$
This is because:
Source: bustle
Version: 0.7.4-1
Vcs-Git: https://salsa.debian.org/haskell-team/DHG_packages.git [p/bustle]
This syntax and its semantics do not appear to be documented in
policy.
Ian.