I'm unable to sign the DCO because the sign-off process is weird, so feel free to consider this a bug report and and use the code as you wish.

@DisposaBoy You just need to use -s flag on commit (git commit -s). The -s flag will add the standard git sign-off message.

You can also use -s with --amend to modify an existing commit that was not signed-off (git commit -s --amend).

Keep in mind that signing-off implies that you accept the DCO.

@smola IMO, the whole process could be simplified to not require contributors to add their email address to commit messages and/or only do it once.
But to be clear, the weird part that I object(ed) to is the bolded part of the following paragraph from your CONTRIBUTING.md

In order to show your agreement with the DCO you should include at the end of commit message, the following line: Signed-off-by: John Doe [email protected], using your real name.

@DisposaBoy Thanks for the clarification. I understand that contributing under a pseudonym is a very legitimate use case. But so far, we are not able to accept that under our current legal guidelines.

I have moved this to an issue: #820
And opened an issue for ourselves to check if we can accept pseudonymous contributions in the future: src-d/guide#208

However, according to our present policy, I have to close this PR.