🪲 Fixed #1008 by documenting new feature in BreakingChanges and removing references to removed features.

Author: mvandervoord

docs/BreakingChanges.md

@@ -181,6 +181,16 @@ In addition, a previously undocumented feature for merging a second configuratio
 
 Thorough documentation on Mixins and the new options for loading a project configuration can be found in _[CeedlingPacket](CeedlingPacket.md))_.
 
+## Replaced `options:` files, environment project specifications, and nested project files with comprehensive `mixins` feature
+
+The following features have all been removed from Ceedling's functionality. No need to worry, though. The new `mixins` feature can handle all the situations these features previously supported, and much more. Check out the [documentation](CeedlingPacket.md) for more detail.
+
+ - `options:blah.yml` command-line options (see `--mixin` command line option)
+ - The corresponding `options_paths:` key in the project.yml file no longer has any effect. (see `:mixins:` ➡️ `:load_paths:` project.yml specification)
+ - The `project.yml` file now specifies other yaml files to load using the `:mixins:` ➡️ `:enabled:` section
+ - `CEEDLING_PROJECT_FILE` environment variable (see `CEEDLING_MIXIN_#` specification)
+ - `CEEDLING_SER_FILE` environment variable (see `CEEDLING_MIXIN_#` specification)
+
 ## Tool definition inline Ruby evaluation replacement removed (inline Ruby string expansion remains)
 
 Reaching back to the earliest days of Ceedling, tool definitions supported two slightly different string replacement options that executed at different points in a build’s lifetime. Yeah. It was maybe not great.

docs/CeedlingPacket.md

@@ -3010,9 +3010,6 @@ and migrated to the `:test_build` and `:release_build` sections.
   :build_root: project_awesome/build
   :use_exceptions: FALSE
   :use_test_preprocessor: :all
-  :options_paths:
-    - project/options
-    - external/shared/options
   :release_build: TRUE
   :compile_threads: :auto
 ```

plugins/dependencies/example/boss/project.yml

@@ -27,9 +27,6 @@
   :test_threads: 8
   :compile_threads: 8
 
-  # you can specify different yaml config files which modify the existing one
-  :options_paths: []
-
   # enable release build (more details in release_build section below)
   :release_build: TRUE
 

plugins/dependencies/example/supervisor/project.yml

@@ -27,9 +27,6 @@
   :test_threads: 8
   :compile_threads: 8
 
-  # you can specify different yaml config files which modify the existing one
-  :options_paths: []
-
   # enable release build (more details in release_build section below)
   :release_build: TRUE