I think that an empty git repository has to be created by Carnë (or colleagues) so that the last command can succeed.
git clone https://github.com/frej/fast-export.git
hg clone ssh://address@hidden/p/octave/divand
../fast-export/hg-fast-export.sh -r ../octave-divand
git log # all looks fine
git remote add origin ssh://address@hidden/p/octave/divand
git config branch.master.remote origin
git config branch.master.merge refs/heads/master
git push origin master
The authenticity of host 'git.code.sf.net
(188.8.131.52)' can't be established.
RSA key fingerprint is 86:7b:1b:12:85:35:8a:b7:98:b6:d2:97:5e:96:58:1d.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'git.code.sf.net
,184.108.40.206' (RSA) to the list of known hosts.
X11 forwarding request failed on channel 0
fatal: '/git/p/octave/divand' does not appear to be a git repository
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.