Add README to the solutions dir

CHANGELOG.md

@@ -13,6 +13,7 @@ cargo install rustlings
 - Fix `rust-analyzer` rebuilding all exercises after changing one file.
 - Show a helpful error message when trying to install Rustlings with a Rust version lower than the minimum one that Rustlings supports.
 - Remove the state file and the solutions directory from the generated `.gitignore` file.
+- Add a `README.md` file to the `solutions/` directory.
 - Run the final check of all exercises in parallel.
 - Small exercise improvements.
 - `dev check`: Check that all solutions are formatted with `rustfmt`.

solutions/README.md

@@ -0,0 +1,6 @@
+# Official Rustlings solutions
+
+Before you finish an exercise, its solution file will only contain an empty `main` function.
+The content of this file will be automatically replaced by the actual solution once you finish the exercise.
+
+Note that these solution are often only _one possibility_ to solve an exercise.

src/init.rs

@@ -35,6 +35,11 @@ pub fn init() -> Result<()> {
         .context("Failed to initialize the `rustlings/exercises` directory")?;
 
     create_dir("solutions").context("Failed to create the `solutions/` directory")?;
+    fs::write(
+        "solutions/README.md",
+        include_bytes!("../solutions/README.md"),
+    )
+    .context("Failed to create the file rustlings/solutions/README.md")?;
     for dir in EMBEDDED_FILES.exercise_dirs {
         let mut dir_path = String::with_capacity(10 + dir.name.len());
         dir_path.push_str("solutions/");