Add the `--field-separator` flag to knife show commands

For the commands that allow you to filter which attributes it shows you
using the `--attribute` flag, add the `--field-separator` flag to allow
the user to customize which character(s) they want to use to deliniate the
attribute hierarchy.

```shell
knife node show NODE -S: -a "packages:Chef Client v12.12.15"
```

Signed-off-by: Tom Duffield <tom@chef.io>

4 files changed, 51 insertions, 6 deletions

diff --git a/lib/chef/knife/core/generic_presenter.rb b/lib/chef/knife/core/generic_presenter.rb
index a963a24f12..861bf1510d 100644
--- a/lib/chef/knife/core/generic_presenter.rb
+++ b/lib/chef/knife/core/generic_presenter.rb
@@ -28,6 +28,11 @@ class Chef
         # :nodoc:
         def self.included(includer)
           includer.class_eval do
+            option :field_separator,
+              :short => "-S SEPARATOR",
+              :long => "--field-separator SEPARATOR",
+              :description => "Character separator used to delineate nesting in --attribute filters (default \".\")"
+
             option :attribute,
               :short => "-a ATTR1 [-a ATTR2]",
               :long => "--attribute ATTR1 [--attribute ATTR2] ",
@@ -175,8 +180,15 @@ class Chef
           config[:attribute] || config[:run_list]
         end
 
+        # GenericPresenter is used in contexts where MultiAttributeReturnOption
+        # is not, so we need to set the default value here rather than as part
+        # of the CLI option.
+        def attribute_field_separator
+          config[:field_separator] || "."
+        end
+
         def extract_nested_value(data, nested_value_spec)
-          nested_value_spec.split(".").each do |attr|
+          nested_value_spec.split(attribute_field_separator).each do |attr|
             data =
               if data.is_a?(Array)
                 data[attr.to_i]
diff --git a/spec/integration/knife/environment_show_spec.rb b/spec/integration/knife/environment_show_spec.rb
index e74bf6d05d..56422dc1a5 100644
--- a/spec/integration/knife/environment_show_spec.rb
+++ b/spec/integration/knife/environment_show_spec.rb
@@ -26,7 +26,7 @@ describe "knife environment show", :workstation do
   when_the_chef_server "has some environments" do
     before do
       environment "b", {
-        "default_attributes" => { "foo" => "bar" },
+        "default_attributes" => { "foo" => "bar", "baz" => { "raz.my" => "mataz" } },
       }
     end
 
@@ -36,6 +36,8 @@ describe "knife environment show", :workstation do
 chef_type:           environment
 cookbook_versions:
 default_attributes:
+  baz:
+    raz.my: mataz
   foo: bar
 description:         
 json_class:          Chef::Environment
@@ -46,11 +48,29 @@ EOM
     # rubocop:enable Style/TrailingWhitespace
 
     it "shows the requested attribute of an environment" do
-      pending "KnifeSupport doesn't appear to pass this through correctly"
-      knife("environment show b -a foo").should_succeed <<EOM
+      knife("environment show b -a default_attributes").should_succeed <<EOM
 b:
-  foo: bar
+  default_attributes:
+    baz:
+      raz.my: mataz
+    foo: bar
 EOM
     end
+
+    it "shows the requested nested attribute of an environment" do
+      knife("environment show b -a default_attributes.baz").should_succeed <<EON
+b:
+  default_attributes.baz:
+    raz.my: mataz
+EON
+    end
+
+    it "shows the requested attribute of an environment with custom field separator" do
+      knife("environment show b -S: -a default_attributes:baz").should_succeed <<EOT
+b:
+  default_attributes:baz:
+    raz.my: mataz
+EOT
+    end
   end
 end
diff --git a/spec/support/shared/integration/knife_support.rb b/spec/support/shared/integration/knife_support.rb
index 1a374e1b84..4efa30a003 100644
--- a/spec/support/shared/integration/knife_support.rb
+++ b/spec/support/shared/integration/knife_support.rb
@@ -64,8 +64,11 @@ module KnifeSupport
         subcommand_class.load_deps
         instance = subcommand_class.new(args)
 
+        # Load configs
+        instance.merge_configs
+
         # Capture stdout/stderr
-        instance.ui = Chef::Knife::UI.new(stdout, stderr, stdin, disable_editing: true)
+        instance.ui = Chef::Knife::UI.new(stdout, stderr, stdin, instance.config.merge(disable_editing: true))
 
         # Don't print stuff
         Chef::Config[:verbosity] = ( DEBUG ? 2 : 0 )
diff --git a/spec/unit/knife/core/ui_spec.rb b/spec/unit/knife/core/ui_spec.rb
index be77fd8501..38c72161e5 100644
--- a/spec/unit/knife/core/ui_spec.rb
+++ b/spec/unit/knife/core/ui_spec.rb
@@ -28,6 +28,7 @@ describe Chef::Knife::UI do
       :verbosity => 0,
       :yes => nil,
       :format => "summary",
+      :field_separator => ".",
     }
     @ui = Chef::Knife::UI.new(@out, @err, @in, @config)
     Chef::Config[:treat_deprecation_warnings_as_errors] = false
@@ -410,6 +411,15 @@ EOM
         @ui.config[:attribute] = non_existing_path
         expect(@ui.format_for_display(input)).to eq({ "sample-data-bag-item" => { non_existing_path => nil } })
       end
+
+      describe "when --field-separator is passed" do
+        it "honors that separator" do
+          input = { "keys" => { "with spaces" => { "open" => { "doors" => { "with many.dots" => "when asked" } } } } }
+          @ui.config[:field_separator] = ";"
+          @ui.config[:attribute] = "keys;with spaces;open;doors;with many.dots"
+          expect(@ui.format_for_display(input)).to eq({ nil => { "keys;with spaces;open;doors;with many.dots" => "when asked" } })
+        end
+      end
     end
 
     describe "with --run-list passed" do