Add userspace config.h handling to build script (#2640)

* Add userspace 'config.h' file

* Add more robust docs

* Remove config.h code from drashna userspace

* Spelling error

* Include links to Config Options page

* Remove config.h documentation from userspace doc, as it's no longer needed

build_keyboard.mk

@@ -204,6 +204,10 @@ endif
 # User space stuff
 USER_PATH := users/$(KEYMAP)
 -include $(USER_PATH)/rules.mk
+ifneq ("$(wildcard users/$(KEYMAP)/config.h)","")
+    CONFIG_H += users/$(KEYMAP)/config.h
+endif
+
 
 # Object files directory
 #     To put object files in current directory, use a dot (.), do NOT make

docs/feature_userspace.md

@@ -3,10 +3,11 @@
 If you use more than one keyboard with a similar keymap, you might see the benefit in being able to share code between them. Create your own folder in `users/` named the same as your keymap (ideally your github username, `<name>`) with the following structure:
 
 * `/users/<name>/` (added to the path automatically)
-  * `readme.md`
+  * `readme.md` (optional, recommended)
   * `rules.mk` (included automatically)
   * `<name>.h` (optional)
   * `<name>.c` (optional)
+  * `config.h` (optional)
 
 `<name>.c` will need to be added to the SRC in `rules.mk` like this:
 
@@ -24,10 +25,31 @@ For example,
 
 Will include the `/users/jack/` folder in the path, along with `/users/jack/rules.mk`.
 
+Additionally, `config.h` here will be processed like the same file in your keymap folder.  This is handled separately from the `<name>.h` file.  
+
+The reason for this, is that `<name>.h` won't be added in time to add settings (such as `#define TAPPING_TERM 100`), and including the `<name.h>` file in any `config.h` files will result in compile issues. 
+
+So you should use the `config.h` for QMK settings, and the `<name>.h` file for user or keymap specific settings. 
+ 
 ## Readme
 
 Please include authorship (your name, github username, email), and optionally [a license that's GPL compatible](https://www.gnu.org/licenses/license-list.html#GPLCompatibleLicenses).
 
+## `Config.h`
+
+If you do add a `config,h` file, you want to make sure that it only gets processed once.  So you may want to start off with something like this: 
+
+```c
+#ifndef USERSPACE_CONFIG_H
+#define USERSPACE_CONFIG_H
+
+// Put normal config.h settings here:
+
+#endif // !USERSPACE_CONFIG_H
+```
+
+You can use any option hre that you could use in your keymap's `config.h` file. You can find a list of vales [here](config_options.md). 
+
 ## Example
 
 For a brief example, checkout `/users/_example/` , or for a more detailed examples check out [`template.h`](https://github.com/qmk/qmk_firmware/blob/master/users/drashna/template.h) and [`template.c`](https://github.com/qmk/qmk_firmware/blob/master/users/drashna/template.c) in `/users/drashna/` .

users/drashna/readme.md

@@ -3,33 +3,6 @@ Overview
 
 This is my personal userspace file.  Most of my code exists here, as it's heavily shared. 
 
-Userspace Config.h
-------------------
-
-By default, the userspace feature doesn't include a `config.h` file the way that that keyboards, revisions, keymaps and layouts handle them.  This means that if you want global configurations via userspace, it's very difficult to implement.  
-
-The reason for using seperate files here is that the `drashna.h` file doesn't get called in such a way that will actually define QMK settings.  Additionally, attempting to add it to the `config.h` files has issues. Namely, the `drashna.h` file requires the `quantum.h` file... but including this to the `config.h` attemps to redefines a bunch of settings and breaks the firmare.  Removing the `quantum.h` include means that a number of data structures no longer get added, and the `SAFE_RANGE` value is no longer defined, as well.  So we need both a `config.h` for global config, and we need a seperate h file for local settings. 
-
-However, the `rules.mk` file is included when building the firmware.  So we can hijack that process to "manually" add a `config.h`. To do so, you would need to add the following to the `rules.mk` in your userspace:
-
-```c
-ifneq ("$(wildcard users/$(KEYMAP)/config.h)","")
-    CONFIG_H += users/$(KEYMAP)/config.h
-endif
-```
-
-You can replace `$(KEYMAP)` with your name, but it's not necessary. This checks for the existence of `/users/<name>/config.h`, and if it exists, includes it like every other `config.h` file, allowing you to make global `config.h` settings. 
-
-As for the `config.h` file, you want to make sure that it has an "ifdef" in it to make sure it's only used once.  So you want something like this: 
-
-```c
-#ifndef USERSPACE_CONFIG_H
-#define USERSPACE_CONFIG_H
-
-// put stuff here 
-
-#endif
-```
 
 Custom userspace handlers
 -------------------------

users/drashna/rules.mk

@@ -2,10 +2,4 @@
 SRC += drashna.c
 EXTRAFLAGS        += -flto
 
-ifneq ("$(wildcard users/$(KEYMAP)/config.h)","")
-    CONFIG_H += users/$(KEYMAP)/config.h
-endif
 
-ifeq ($(strip $(NO_SECRETS)), yes)
-    OPT_DEFS += -DNO_SECRETS
-endif