rustc: add lint level cli ordering into the documentation

Author: tobithiel

src/doc/rustc/src/command-line-arguments.md

@@ -215,21 +215,29 @@ This controls which [target](targets/index.md) to produce.
 
 This flag will set which lints should be set to the [warn level](lints/levels.md#warn).
 
+_Note:_ The order of these lint level arguments is taken into account, see [lint level via compiler flag](lints/levels.md#via-compiler-flag) for more information.
+
 <a id="option-a-allow"></a>
 ## `-A`: set lint allowed
 
 This flag will set which lints should be set to the [allow level](lints/levels.md#allow).
 
+_Note:_ The order of these lint level arguments is taken into account, see [lint level via compiler flag](lints/levels.md#via-compiler-flag) for more information.
+
 <a id="option-d-deny"></a>
 ## `-D`: set lint denied
 
 This flag will set which lints should be set to the [deny level](lints/levels.md#deny).
 
+_Note:_ The order of these lint level arguments is taken into account, see [lint level via compiler flag](lints/levels.md#via-compiler-flag) for more information.
+
 <a id="option-f-forbid"></a>
 ## `-F`: set lint forbidden
 
 This flag will set which lints should be set to the [forbid level](lints/levels.md#forbid).
 
+_Note:_ The order of these lint level arguments is taken into account, see [lint level via compiler flag](lints/levels.md#via-compiler-flag) for more information.
+
 <a id="option-z-unstable"></a>
 ## `-Z`: set unstable options
 

src/doc/rustc/src/lints/levels.md

@@ -164,6 +164,18 @@ And of course, you can mix these four flags together:
 $ rustc lib.rs --crate-type=lib -D missing-docs -A unused-variables
 ```
 
+The order of these command line arguments is taken into account. The following allows the `unused-variables` lint, because it is the last argument for that lint:
+
+```bash
+$ rustc lib.rs --crate-type=lib -D unused-variables -A unused-variables
+```
+
+You can make use of this behavior by overriding the level of one specific lint out of a group of lints. The following example denies all the lints in the `unused` group, but explicitly allows the `unused-variables` lint in that group:
+
+```bash
+$ rustc lib.rs --crate-type=lib -D unused -A unused-variables
+```
+
 ### Via an attribute
 
 You can also modify the lint level with a crate-wide attribute: