preserve-environments using r10k deployed environments not working

> Description of problem

- What did you do?
I am trying to run octocatalog-diff on a puppetserver running puppet 4.10.12 with puppet environments managed by r10k in the following structure:
`/etc/puppetlabs/puppet
- environments
- production
- environment.conf
- manifests
- site.pp
- modules
- site
- staging
- environment.conf
- manifests
- site.pp
- modules
- site
- testing_branch
- environment.conf
- manifests
- site.pp
- modules
- site`
I am trying to run octocatalog-diff against the checked out code using the --preserve-environments option as follows:
- What happened?
octocatalog-diff exits with an error code 1, expecting a basedir configuration specified, which isn't required as per [documentation on advanced environments](https://github.com/github/octocatalog-diff/blob/master/doc/advanced-environments.md)
- What did you expect to happen?
I expected octocatalog-diff to create and compare catalogues created from the two r10k deployed environments.
Puppet agent runs against both environments work as expected.
- How can someone reproduce the problem?
Create two different working puppet environments and run octocatalog-diff as explained above
> Command used and debugging output

`octocatalog-diff -n [nodename] --bootstrapped-from-dir /etc/puppetlabs/puppet --bootstrapped-to-dir /etc/puppetlabs/puppet --from-environment production --to-environment testing_branch --preserve-environments`
`D, [2018-06-13T17:07:41.649263 #24328] DEBUG -- : Running octocatalog-diff 1.5.3 with ruby 2.1.5
D, [2018-06-13T17:07:41.649465 #24328] DEBUG -- : Command line arguments: ["-n", "node_name", "--bootstrapped-from-dir", "/etc/puppetlabs/puppet", "--bootstrapped-to-dir", "/etc/puppetlabs/puppet", "--from-environment", "production", "--to-environment", "testing_branch", "--preserve-environments", "-d"]
D, [2018-06-13T17:07:41.649552 #24328] DEBUG -- : Running on host puppetserver_name (x86_64-linux-gnu)
/var/lib/gems/2.1.0/gems/octocatalog-diff-1.5.3/lib/octocatalog-diff/catalog-util/git.rb:63:in `fetch': key not found: :basedir (KeyError)
from /var/lib/gems/2.1.0/gems/octocatalog-diff-1.5.3/lib/octocatalog-diff/catalog-util/git.rb:63:in `branch_sha'
from /var/lib/gems/2.1.0/gems/octocatalog-diff-1.5.3/lib/octocatalog-diff/catalog-util/cached_master_directory.rb:112:in `git_repo_checkout_bootstrap'
from /var/lib/gems/2.1.0/gems/octocatalog-diff-1.5.3/lib/octocatalog-diff/catalog-util/cached_master_directory.rb:49:in `run'
from /var/lib/gems/2.1.0/gems/octocatalog-diff-1.5.3/lib/octocatalog-diff/cli.rb:106:in `cli'
from /var/lib/gems/2.1.0/gems/octocatalog-diff-1.5.3/bin/octocatalog-diff:34:in `'
from /usr/local/bin/octocatalog-diff:23:in `load'
from /usr/local/bin/octocatalog-diff:23:in `'
`

> Platform and version information

- Your OS: Debian Linux 8 (Jessie)
- Your Ruby version: ruby 2.1.5p273 (2014-11-13) [x86_64-linux-gnu]
- Your version of Puppet: puppet 4.10.12 OSE
- Your version of octocatalog-diff: octocatalog-diff 1.5.3

> Do the tests pass from a clean checkout?
yes

> Anything else to add that you think will be helpful?
When I add the -f and -t options, the catalog compiles, but then I get errors about custom providers not found:
command:
`octocatalog-diff -n node_name --bootstrapped-from-dir /etc/puppetlabs/puppet/environments/production --bootstrapped-to-dir /etc/puppetlabs/puppet/environments/testing_branch --from-environment production --to-environment testing_branch -f production -t testing_branch -d`
catalog error:
`Error: Could not autoload puppet/provider/network_config/interfaces: cannot load such file -- puppetx/filemapper
Error: Could not autoload puppet/type/network_config: Could not autoload puppet/provider/network_config/interfaces: cannot load such file -- puppetx/filemapper
Error: Evaluation Error: Error while evaluating a Resource Statement, Evaluation Error: Error while evaluating a Resource Statement, Could not autoload puppet/type/network_config: Could not autoload puppet/provider/network_config/interfaces: cannot load such file -- puppetx/filemapper at /tmp/ocd-ipc-20180613-28056-1iximb4/ocd-builddir-20180613-28061-30pfww/environments/testing_branch/modules/monolith/quotaman/manifests/config.pp:80:3 on node quotaman-staging3.cpt3.host-h.net
Error: Evaluation Error: Error while evaluating a Resource Statement, Evaluation Error: Error while evaluating a Resource Statement, Could not autoload puppet/type/network_config: Could not autoload puppet/provider/network_config/interfaces: cannot load such file -- puppetx/filemapper at /tmp/ocd-ipc-20180613-28056-1iximb4/ocd-builddir-20180613-28061-30pfww/environments/testing_branch/modules/monolith/quotaman/manifests/config.pp:80:3 on node quotaman-staging3.cpt3.host-h.net
Error: Failed to compile catalog for node quotaman-staging3.cpt3.host-h.net: Evaluation Error: Error while evaluating a Resource Statement, Evaluation Error: Error while evaluating a Resource Statement, Could not autoload puppet/type/network_config: Could not autoload puppet/provider/network_config/interfaces: cannot load such file -- puppetx/filemapper at /tmp/ocd-ipc-20180613-28056-1iximb4/ocd-builddir-20180613-28061-30pfww/environments/testing_branch/modules/monolith/quotaman/manifests/config.pp:80:3 on node node_name`

Inizia da lib/octocatalog-diff/catalog-util/git.rb:63 e dal flusso delle chiamate in lib/octocatalog-diff/catalog-util/cached_master_directory.rb. Riproduci il comando --preserve-environments documentato nell’issue e confronta la relativa gestione con advanced-environments.md. Il lavoro è completato quando i due ambienti r10k possono essere confrontati senza l’errore dovuto a :basedir mancante.

Scritto dal modello di indicizzazione a partire dal testo della issue.