Implement `hx --tutor` and `:tutor` to load `tutor.txt` (#898)

* Implement `hx --tutor` and `:tutor` to load `tutor.txt`

* Document `hx --tutor` and `:tutor`

* Change `Document::set_path` to take an `Option`

* `Document::set_path` accepts an `Option<&Path>` instead of `&Path`.
* Remove `Editor::open_tutor` and make tutor-open functionality use
  `Editor::open` and `Document::set_path`.

* Use `PathBuf::join`

Co-authored-by: Ivan Tham <pickfire@riseup.net>

* Add comments explaining unsetting tutor path

Co-authored-by: Ivan Tham <pickfire@riseup.net>

1 files changed, 8 insertions, 4 deletions

diff --git a/helix-view/src/document.rs b/helix-view/src/document.rs
index b0257f03..4d779656 100644
--- a/helix-view/src/document.rs
+++ b/helix-view/src/document.rs
@@ -368,7 +368,7 @@ impl Document {
         let mut doc = Self::from(rope, Some(encoding));
 
         // set the path and try detecting the language
-        doc.set_path(path)?;
+        doc.set_path(Some(path))?;
         if let Some(loader) = config_loader {
             doc.detect_language(theme, loader);
         }
@@ -553,12 +553,16 @@ impl Document {
         self.encoding
     }
 
-    pub fn set_path(&mut self, path: &Path) -> Result<(), std::io::Error> {
-        let path = helix_core::path::get_canonicalized_path(path)?;
+    pub fn set_path(&mut self, path: Option<&Path>) -> Result<(), std::io::Error> {
+        let path = if let Some(p) = path {
+            Some(helix_core::path::get_canonicalized_path(p)?)
+        } else {
+            path.map(|p| p.into())
+        };
 
         // if parent doesn't exist we still want to open the document
         // and error out when document is saved
-        self.path = Some(path);
+        self.path = path;
 
         Ok(())
     }