Thanks for the quick response Nick,
I think I was setting the version wrong, I was setting a version number when it needs to be the branch (?), your link to the composer docs pointed me in the right direction.
For future reference for others, this worked:
Your project’s composer.json needs:
{
"type": "vcs",
"url": "git@bitbucket.org:accountname/reponame.git"
}
in your repositories list,
"accountname/reponame":"dev-master"
listed as a requirement and your external plugin only needs to contain:
{
"name": "accountname/reponame",
"version": "master",
"type": "wordpress-plugin",
"dist": {
"url": "git@bitbucket.org:accountname/reponame.git",
"type": "git"
}
}