change the way branch permalinks work

branch permalinks still use /b, but /b?abc now acts as a redirect rather than doing annoying JavaScript garbage
I changed the branch element ID format to accomodate this---now the IDs are of form `b-{id}` rather than `{tree_path}:{id}`.
the old way was stupid anyways.

I hope nothing breaks too majorly because of this.

crates/treehouse/src/cli/serve.rs

@@ -23,7 +23,7 @@ use tracing::{info, instrument};
 use crate::dirs::Dirs;
 use crate::sources::Sources;
 use crate::vfs::asynch::AsyncDir;
-use crate::vfs::VPath;
+use crate::vfs::{self, VPath};
 use crate::{html::EscapeHtml, state::Source};
 
 mod system {
@@ -159,36 +159,12 @@ async fn branch(RawQuery(named_id): RawQuery, State(state): State<Arc<Server>>)
             });
         if let Some(branch_id) = branch_id {
             let branch = state.sources.treehouse.tree.branch(branch_id);
-            if let Source::Tree { input, tree_path } =
-                state.sources.treehouse.source(branch.file_id)
-            {
-                if let Some(content) = state
-                    .target
-                    .content(tree_path)
-                    .await
-                    .and_then(|c| c.string().ok())
+            if let Source::Tree { tree_path, .. } = state.sources.treehouse.source(branch.file_id) {
+                if let Some(url) =
+                    vfs::url(&state.sources.config.site, &state.target.sync(), tree_path)
                 {
-                    let branch_markup = input[branch.content.clone()].trim();
-                    let mut per_page_metadata =
-                        String::from("<meta property=\"og:description\" content=\"");
-                    write!(per_page_metadata, "{}", EscapeHtml(branch_markup)).unwrap();
-                    per_page_metadata.push_str("\">");
-                    per_page_metadata.push_str(r#"<meta name="robots" content="noindex">"#);
-
-                    const PER_PAGE_METADATA_REPLACEMENT_STRING: &str = "<!-- treehouse-ca37057a-cff5-45b3-8415-3b02dbf6c799-per-branch-metadata -->";
-                    return Html(content.replacen(
-                        PER_PAGE_METADATA_REPLACEMENT_STRING,
-                        &per_page_metadata,
-                        // Replace one under the assumption that it appears in all pages.
-                        1,
-                    ))
-                    .into_response();
-                } else {
-                    return (
-                        StatusCode::INTERNAL_SERVER_ERROR,
-                        format!("500 Internal Server Error: branch metadata points to entry {tree_path} which does not have readable content")
-                    )
-                        .into_response();
+                    let url = format!("{url}#{}", branch.html_id);
+                    return (StatusCode::FOUND, [(LOCATION, url)]).into_response();
                 }
             }
         }

crates/treehouse/src/generate.rs

@@ -19,8 +19,8 @@ use crate::{
     fun::seasons::Season,
     sources::Sources,
     vfs::{
-        self, Cd, Content, ContentCache, Dir, DynDir, Entries, HtmlCanonicalize, MemDir, Overlay,
-        ToDynDir, VPath, VPathBuf,
+        self, AnchoredAtExt, Cd, Content, ContentCache, Dir, DynDir, Entries, HtmlCanonicalize,
+        MemDir, Overlay, ToDynDir, VPath, VPathBuf,
     },
 };
 
@@ -230,5 +230,7 @@ pub fn target(dirs: Arc<Dirs>, sources: Arc<Sources>) -> DynDir {
     tree_view.warm_up();
     let tree_view = HtmlCanonicalize::new(tree_view);
 
-    Overlay::new(tree_view.to_dyn(), root.to_dyn()).to_dyn()
+    Overlay::new(tree_view.to_dyn(), root.to_dyn())
+        .anchored_at(VPath::ROOT.to_owned())
+        .to_dyn()
 }

crates/treehouse/src/tree.rs

@@ -184,11 +184,7 @@ impl SemaBranch {
         let attributes = Self::parse_attributes(treehouse, diagnostics, config, file_id, &branch);
 
         let named_id = attributes.id.to_owned();
-        let html_id = format!(
-            "{}:{}",
-            treehouse.tree_path(file_id).unwrap(),
-            attributes.id
-        );
+        let html_id = format!("b-{}", attributes.id);
 
         let redirect_here = attributes.redirect_here.clone();
 

crates/treehouse/src/vfs/asynch.rs

@@ -10,6 +10,10 @@ impl AsyncDir {
         Self { inner }
     }
 
+    pub fn sync(&self) -> &DynDir {
+        &self.inner
+    }
+
     pub async fn content(&self, path: &VPath) -> Option<Content> {
         let this = self.clone();
         let path = path.to_owned();