Auto merge of #6915 - smoelius:docs-link, r=llogiq

Do not show docs link when lint doesn't start with "clippy::"

This small change ensures that if the diagnostic functions are called from outside of Clippy, a docs link is not displayed.

---

*Please write a short comment explaining your change (or "none" for internal only changes)*
changelog: restrict docs links

Author: bors

clippy_utils/src/diagnostics.rs

@@ -8,14 +8,16 @@ use std::env;
 
 fn docs_link(diag: &mut DiagnosticBuilder<'_>, lint: &'static Lint) {
     if env::var("CLIPPY_DISABLE_DOCS_LINKS").is_err() {
-        diag.help(&format!(
-            "for further information visit https://rust-lang.github.io/rust-clippy/{}/index.html#{}",
-            &option_env!("RUST_RELEASE_NUM").map_or("master".to_string(), |n| {
-                // extract just major + minor version and ignore patch versions
-                format!("rust-{}", n.rsplitn(2, '.').nth(1).unwrap())
-            }),
-            lint.name_lower().replacen("clippy::", "", 1)
-        ));
+        if let Some(lint) = lint.name_lower().strip_prefix("clippy::") {
+            diag.help(&format!(
+                "for further information visit https://rust-lang.github.io/rust-clippy/{}/index.html#{}",
+                &option_env!("RUST_RELEASE_NUM").map_or("master".to_string(), |n| {
+                    // extract just major + minor version and ignore patch versions
+                    format!("rust-{}", n.rsplitn(2, '.').nth(1).unwrap())
+                }),
+                lint
+            ));
+        }
     }
 }