[vcpkg-docs] Add feature packages to core documentation of CONTROL files

2 files changed, 49 insertions, 6 deletions

diff --git a/docs/maintainers/control-files.md b/docs/maintainers/control-files.md
index 17cb50311..eb03f1d94 100644
--- a/docs/maintainers/control-files.md
+++ b/docs/maintainers/control-files.md
@@ -1,16 +1,29 @@
 # CONTROL files
+
 Each port has some static metadata in the form of a `CONTROL` file. This file uses the same syntax and a subset of the fields from [the Debian `control` format][debian].
 
 Field names are case-sensitive.
 
 [debian]: https://www.debian.org/doc/debian-policy/ch-controlfields.html
 
-## Recognized fields
+## Source Paragraph
+
+The first paragraph appearing in a `CONTROL` file is the Source paragraph, which defines the core attributes of the package (name, version, and so on).
+
+### Example:
+```no-highlight
+Source: vtk
+Version: 8.1.0-1
+Description: Software system for 3D computer graphics, image processing, and visualization
+Build-Depends: zlib, libpng, tiff, libxml2, jsoncpp, glew, freetype
+```
+
+### Recognized fields
 
-### Source
+#### Source
 The name of the port.
 
-### Version
+#### Version
 The port version.
 
 This field should be an alphanumeric string which may also contain `.`, `_`, or `-`. No attempt at ordering versions is made; all versions are treated as bitstrings and are only evaluated for equality.
@@ -22,15 +35,15 @@ Example:
 Version: 1.0.5-2
 ```
 
-### Description
+#### Description
 A description of the library
 
 The first sentence of the description should concisely describe the purpose and contents of the library. Then, a larger description including the library's "proper name" should follow.
 
-### Maintainer
+#### Maintainer
 Reserved for future use.
 
-### Build-Depends
+#### Build-Depends
 The list of dependencies required to build and use this library.
 
 Example:
@@ -49,3 +62,31 @@ Example:
 Build-Depends: zlib (windows), openssl (windows), boost (windows), websocketpp (windows)
 ```
 
+## Feature Paragraphs
+
+After the Source Paragraph, `CONTROL` files can list zero or more Feature Paragraphs which declare features.
+
+### Example:
+```no-highlight
+Source: vtk
+Version: 8.1.0-1
+Description: Software system for 3D computer graphics, image processing, and visualization
+Build-Depends: zlib, libpng, tiff, libxml2, jsoncpp, glew, freetype
+
+Feature: mpi
+Description: MPI functionality for VTK
+Build-Depends: msmpi, hdf5[parallel]
+```
+
+### Recognized fields
+
+#### Feature
+The name of the feature.
+
+#### Description
+A description of the feature
+
+#### Build-Depends
+The list of dependencies required to build and use this feature.
+
+All dependencies from selected features are unioned together to produce the final dependency set for the build. This field follows the same syntax as `Build-Depends` in the Source Paragraph.
diff --git a/docs/specifications/feature-packages.md b/docs/specifications/feature-packages.md
index 2c7f60ff9..198a602ba 100644
--- a/docs/specifications/feature-packages.md
+++ b/docs/specifications/feature-packages.md
@@ -1,5 +1,7 @@
 # Proposal: Features / Feature packages (Feb 23 2017)

 

+**Note: this is the proposal as it was initially accepted and does not neccessarily reflect the current behavior.**

+

 ## 1. Motivation

 

 ### A. OpenCV + CUDA