Auto merge of #10712 - blyxyas:fix-fixflag_implies_all_targets, r=llogiq

Document that `cargo clippy --fix` implies `--all-targets`

In [`cargo fix`'s documentation](https://doc.rust-lang.org/cargo/commands/cargo-fix.html) they indicate that `fix` implies `--all-targets` if no target is supplied. As Clippy uses Cargo under the hood, this also applies to Clippy, but we didn't document that behaviour.

This PR changes that

Fixes #10690
changelog: Add to documentation that `--fix` implies `--all-targets`

Author: bors

README.md

@@ -91,7 +91,8 @@ cargo clippy
 
 #### Automatically applying Clippy suggestions
 
-Clippy can automatically apply some lint suggestions, just like the compiler.
+Clippy can automatically apply some lint suggestions, just like the compiler. Note that `--fix` implies
+`--all-targets`, so it can fix as much code as it can.
 
 ```terminal
 cargo clippy --fix

book/src/usage.md

@@ -111,7 +111,8 @@ fn main() {
 
 ### Automatically applying Clippy suggestions
 
-Clippy can automatically apply some lint suggestions, just like the compiler.
+Clippy can automatically apply some lint suggestions, just like the compiler. Note that `--fix` implies
+`--all-targets`, so it can fix as much code as it can.
 
 ```terminal
 cargo clippy --fix

lintcheck/README.md

@@ -79,9 +79,11 @@ is explicitly specified in the options.
 
 ### Fix mode
 You can run `cargo lintcheck --fix` which will run Clippy with `--fix` and
-print a warning if Clippy's suggestions fail to apply (if the resulting code does not build).  
+print a warning if Clippy's suggestions fail to apply (if the resulting code does not build). 
 This lets us spot bad suggestions or false positives automatically in some cases.  
 
+> Note: Fix mode implies `--all-targets`, so it can fix as much code as it can.
+
 Please note that the target dir should be cleaned afterwards since clippy will modify
 the downloaded sources which can lead to unexpected results when running lintcheck again afterwards.
 

src/main.rs

@@ -13,7 +13,7 @@ Usage:
 
 Common options:
     --no-deps                Run Clippy only on the given crate, without linting the dependencies
-    --fix                    Automatically apply lint suggestions. This flag implies `--no-deps`
+    --fix                    Automatically apply lint suggestions. This flag implies `--no-deps` and `--all-targets`
     -h, --help               Print this message
     -V, --version            Print version info and exit
     --explain LINT           Print the documentation for a given lint