$fill stage (#602)

* initial page setup for fill

* add syntax table

* table formatting

* outline examples

* fix build warning

* fix list casing

* add example with constant value

* active voice

* fix formatting

* cleanup

* fix example formatting

* add second example

* cleanup

* start third example

* finalize third example

* add final example

* highlight lines in last example

* proof reading

* fix line highlighting

* add 'method' link

* add seealso

* add second seealso directive

* updates per copy review

* add missing word

* reformat 'seealso'

* fix bullet format

* add pipeline preface

* updates per opy review

* fix definition for linear fill

* add link to complete example

* add links to examples

* updates per tech review

* linearFill formatting

* tweak

* lowercase with

* add missing commas

* fix hours in example

* fix example output

* add missing word

* formatting

Author: jeff-allen-mongo

source/includes/extracts-agg-stages.yaml

@@ -57,6 +57,10 @@ content: |
           aggregations capable of characterizing data across multiple
           dimensions, or facets, in a single stage.
 
+      * - :pipeline:`$fill`
+
+        - .. include:: /includes/fact-fill-description.rst
+
       * - :pipeline:`$geoNear`
 
         - .. include:: /includes/extracts/geoNear-stage-toc-description.rst

source/includes/fact-fill-description.rst

@@ -0,0 +1 @@
+Populates ``null`` and missing field values within documents.

source/reference/operator/aggregation-pipeline.txt

@@ -118,6 +118,10 @@ Alphabetical Listing of Stages
        input documents. Enables the creation of multi-faceted
        aggregations capable of characterizing data across multiple
        dimensions, or facets, in a single stage.
+
+   * - :pipeline:`$fill`
+
+     - .. include:: /includes/fact-fill-description.rst
 
 
    * - :pipeline:`$geoNear`
@@ -352,6 +356,7 @@ Alphabetical Listing of Stages
    /reference/operator/aggregation/densify
    /reference/operator/aggregation/documents
    /reference/operator/aggregation/facet
+   /reference/operator/aggregation/fill
    /reference/operator/aggregation/geoNear
    /reference/operator/aggregation/graphLookup
    /reference/operator/aggregation/group
@@ -379,4 +384,3 @@ Alphabetical Listing of Stages
    /reference/operator/aggregation/unionWith
    /reference/operator/aggregation/unset
    /reference/operator/aggregation/unwind
-