fix(init): skip existing files instead of erroring (#20434)

### What
Skip writing files from the template if the files already exist in the
project directory.

### Why
When I run deno init in a directory that already has a main.ts, or one
of the other template files, I usually want to initialize a workspace
around a file I've started working in. A hard error in this case seems
counter productive. An informational message about what's being skipped
seems sufficient.

Close #20433

1 files changed, 16 insertions, 7 deletions

diff --git a/cli/tools/init/mod.rs b/cli/tools/init/mod.rs
index f0da86006..9e46359c0 100644
--- a/cli/tools/init/mod.rs
+++ b/cli/tools/init/mod.rs
@@ -14,13 +14,22 @@ fn create_file(
   filename: &str,
   content: &str,
 ) -> Result<(), AnyError> {
-  let mut file = std::fs::OpenOptions::new()
-    .write(true)
-    .create_new(true)
-    .open(dir.join(filename))
-    .with_context(|| format!("Failed to create {filename} file"))?;
-  file.write_all(content.as_bytes())?;
-  Ok(())
+  let path = dir.join(filename);
+  if path.exists() {
+    info!(
+      "ℹ️ {}",
+      colors::gray(format!("Skipped creating {filename} as it already exists"))
+    );
+    Ok(())
+  } else {
+    let mut file = std::fs::OpenOptions::new()
+      .write(true)
+      .create_new(true)
+      .open(path)
+      .with_context(|| format!("Failed to create {filename} file"))?;
+    file.write_all(content.as_bytes())?;
+    Ok(())
+  }
 }
 
 pub async fn init_project(init_flags: InitFlags) -> Result<(), AnyError> {