Import root cert in addition to root key

[dnwake]

This change enables the optional flag --rootcert in addition to --rootkey.

If both --rootcert and --rootkey are specified, then the specified key and cert are both imported as the root keypair, provided they are compatible.

I haven't added a testcase yet, but would appreciate feedback. Thanks.

[GordonTheTurtle]

Please sign your commits following these rules:
https://github.com/docker/docker/blob/master/CONTRIBUTING.md#sign-your-work
The easiest way to do this is to amend the last commit:

$ git clone -b "import_key_and_cert" [email protected]:dnwake/notary.git somewhere
$ cd somewhere
$ git rebase -i HEAD~2
editor opens
change each 'pick' to 'edit'
save the file and quit
$ git commit --amend -s --no-edit
$ git rebase --continue # and repeat the amend for each commit
$ git push -f

Ammending updates the existing PR. You DO NOT need to open a new one.

[GordonTheTurtle]

Please sign your commits following these rules:
https://github.com/docker/docker/blob/master/CONTRIBUTING.md#sign-your-work
The easiest way to do this is to amend the last commit:

$ git clone -b "import_key_and_cert" [email protected]:dnwake/notary.git somewhere
$ cd somewhere
$ git rebase -i HEAD~2
editor opens
change each 'pick' to 'edit'
save the file and quit
$ git commit --amend -s --no-edit
$ git rebase --continue # and repeat the amend for each commit
$ git push -f

Ammending updates the existing PR. You DO NOT need to open a new one.

[docker-jenkins]

Can one of the admins verify this patch?

[GordonTheTurtle]

Please sign your commits following these rules:
https://github.com/docker/docker/blob/master/CONTRIBUTING.md#sign-your-work
The easiest way to do this is to amend the last commit:

$ git clone -b "import_key_and_cert" [email protected]:dnwake/notary.git somewhere
$ cd somewhere
$ git rebase -i HEAD~2
editor opens
change each 'pick' to 'edit'
save the file and quit
$ git commit --amend -s --no-edit
$ git rebase --continue # and repeat the amend for each commit
$ git push -f

Ammending updates the existing PR. You DO NOT need to open a new one.

[GordonTheTurtle]

Please sign your commits following these rules:
https://github.com/docker/docker/blob/master/CONTRIBUTING.md#sign-your-work
The easiest way to do this is to amend the last commit:

$ git clone -b "import_key_and_cert" [email protected]:dnwake/notary.git somewhere
$ cd somewhere
$ git rebase -i HEAD~2
editor opens
change each 'pick' to 'edit'
save the file and quit
$ git commit --amend -s --no-edit
$ git rebase --continue # and repeat the amend for each commit
$ git push -f

Ammending updates the existing PR. You DO NOT need to open a new one.

[dnwake]

Closing until I've been able to do more testing

[dnwake]

I've abandoned this pull request and created another here: #821