chore: Move from master branch to main branch

Author: mokou

install.sh

@@ -115,8 +115,8 @@ then
     if [[ -z ${Version}  ]]
     then
         echo "No valid tag version found"
-        echo "Rustlings will be installed using the master branch"
-        Version="master"
+        echo "Rustlings will be installed using the main branch"
+        Version="main"
     else
         Version="tags/${Version}"
     fi

src/exercise.rs

@@ -134,7 +134,7 @@ path = "{}.rs""#,
                     .expect("Failed to compile!");
                 // Due to an issue with Clippy, a cargo clean is required to catch all lints.
                 // See https://github.com/rust-lang/rust-clippy/issues/2604
-                // This is already fixed on master branch. See this issue to track merging into Cargo:
+                // This is already fixed on Clippy's master branch. See this issue to track merging into Cargo:
                 // https://github.com/rust-lang/rust-clippy/issues/3837
                 Command::new("cargo")
                     .args(&["clean", "--manifest-path", CLIPPY_CARGO_TOML_PATH])

src/main.rs

@@ -132,7 +132,7 @@ fn main() {
         println!("You can also contribute your own exercises to help the greater community!");
         println!();
         println!("Before reporting an issue or contributing, please read our guidelines:");
-        println!("https://github.com/rust-lang/rustlings/blob/master/CONTRIBUTING.md");
+        println!("https://github.com/rust-lang/rustlings/blob/main/CONTRIBUTING.md");
     }
 
     if matches.subcommand_name().is_none() {