Show file preview in split pane in fuzzy finder (#534)

* Add preview pane for fuzzy finder

* Fix picker preview lag by caching

* Add picker preview for document symbols

* Cache picker preview per document instead of view

* Use line instead of range for preview doc

* Add picker preview for buffer picker

* Fix render bug and refactor picker

* Refactor picker preview rendering

* Split picker and preview and compose

The current selected item is cloned on every event, which is
undesirable

* Refactor out clones in previewed picker

* Retrieve doc from editor if possible in filepicker

* Disable syntax highlight for picker preview

Files already loaded in memory have syntax highlighting enabled

* Ignore directory symlinks in file picker

* Cleanup unnecessary pubs and derives

* Remove unnecessary highlight from file picker

* Reorganize buffer rendering

* Use normal picker for code actions

* Remove unnecessary generics and trait impls

* Remove prepare_for_render and make render mutable

* Skip picker preview if screen small, less padding

1 files changed, 2 insertions, 2 deletions

diff --git a/helix-term/src/ui/prompt.rs b/helix-term/src/ui/prompt.rs
index 57daef3a..8ec3674e 100644
--- a/helix-term/src/ui/prompt.rs
+++ b/helix-term/src/ui/prompt.rs
@@ -352,7 +352,7 @@ impl Prompt {
         }
 
         if let Some(doc) = (self.doc_fn)(&self.line) {
-            let text = ui::Text::new(doc.to_string());
+            let mut text = ui::Text::new(doc.to_string());
 
             let viewport = area;
             let area = viewport.intersection(Rect::new(
@@ -546,7 +546,7 @@ impl Component for Prompt {
         EventResult::Consumed(None)
     }
 
-    fn render(&self, area: Rect, surface: &mut Surface, cx: &mut Context) {
+    fn render(&mut self, area: Rect, surface: &mut Surface, cx: &mut Context) {
         self.render_prompt(area, surface, cx)
     }