Split helix_core::find_root and helix_loader::find_local_config_dirs (#3929)

* Split helix_core::find_root and helix_loader::find_local_config_dirs

The documentation of find_root described the following priority for
detecting a project root:
- Top-most folder containing a root marker in current git repository
- Git repository root if no marker detected
- Top-most folder containing a root marker if not git repository detected
- Current working directory as fallback

The commit contained in https://github.com/helix-editor/helix/pull/1249
extracted and changed the implementation of find_root in find_root_impl,
actually reversing its result order (since that is the order that made
sense for the local configuration merge, from innermost to outermost
ancestors).

Since the two uses of find_root_impl have different requirements (and
it's not a matter of reversing the order of results since, e.g., the top
repository dir should be used by find_root only if there's not marker in
other dirs), this PR splits the two implementations in two different
specialized functions.

In doing so, find_root_impl is removed and the implementation is moved
back in find_root, moving it closer to the documented behaviour thus
making it easier to verify it's actually correct

* helix-core: remove Option from find_root return type

It always returns some result, so Option is not needed

1 files changed, 3 insertions, 8 deletions

diff --git a/helix-lsp/src/client.rs b/helix-lsp/src/client.rs
index 9ae8f20e..497ce80c 100644
--- a/helix-lsp/src/client.rs
+++ b/helix-lsp/src/client.rs
@@ -34,7 +34,7 @@ pub struct Client {
     pub(crate) capabilities: OnceCell<lsp::ServerCapabilities>,
     offset_encoding: OffsetEncoding,
     config: Option<Value>,
-    root_path: Option<std::path::PathBuf>,
+    root_path: std::path::PathBuf,
     root_uri: Option<lsp::Url>,
     workspace_folders: Vec<lsp::WorkspaceFolder>,
     req_timeout: u64,
@@ -74,9 +74,7 @@ impl Client {
 
         let root_path = find_root(None, root_markers);
 
-        let root_uri = root_path
-            .clone()
-            .and_then(|root| lsp::Url::from_file_path(root).ok());
+        let root_uri = lsp::Url::from_file_path(root_path.clone()).ok();
 
         // TODO: support multiple workspace folders
         let workspace_folders = root_uri
@@ -281,10 +279,7 @@ impl Client {
             workspace_folders: Some(self.workspace_folders.clone()),
             // root_path is obsolete, but some clients like pyright still use it so we specify both.
             // clients will prefer _uri if possible
-            root_path: self
-                .root_path
-                .clone()
-                .and_then(|path| path.to_str().map(|path| path.to_owned())),
+            root_path: self.root_path.to_str().map(|path| path.to_owned()),
             root_uri: self.root_uri.clone(),
             initialization_options: self.config.clone(),
             capabilities: lsp::ClientCapabilities {