version history MVP

implement basic version history support; there's now an icon in the footer that lets you see the previous versions and their sources
I'm a bit worried about spoilers but honestly it's yet another way to hint yourself at the cool secrets so I don't mind

crates/treehouse/src/state.rs

@@ -1,4 +1,4 @@
-use std::{collections::HashMap, ops::Range};
+use std::{collections::HashMap, ops::Range, path::PathBuf};
 
 use anyhow::Context;
 use codespan_reporting::{
@@ -6,13 +6,27 @@ use codespan_reporting::{
     files::SimpleFiles,
     term::termcolor::{ColorChoice, StandardStream},
 };
+use serde::Serialize;
 use ulid::Ulid;
 
 use crate::tree::{SemaBranchId, SemaRoots, SemaTree};
 
+#[derive(Debug, Clone, Serialize)]
+pub struct RevisionInfo {
+    pub is_latest: bool,
+    pub number: usize,
+    pub commit: String,
+    pub commit_short: String,
+}
+
 #[derive(Debug, Clone)]
 pub enum Source {
-    Tree { input: String, tree_path: String },
+    Tree {
+        input: String,
+        tree_path: String,
+        target_path: PathBuf,
+        revision_info: RevisionInfo,
+    },
     Other(String),
 }
 
@@ -37,7 +51,6 @@ pub type FileId = <Files as codespan_reporting::files::Files<'static>>::FileId;
 /// Treehouse compilation context.
 pub struct Treehouse {
     pub files: Files,
-    pub diagnostics: Vec<Diagnostic<FileId>>,
 
     pub tree: SemaTree,
     pub branches_by_named_id: HashMap<String, SemaBranchId>,
@@ -52,7 +65,6 @@ impl Treehouse {
     pub fn new() -> Self {
         Self {
             files: Files::new(),
-            diagnostics: vec![],
 
             tree: SemaTree::default(),
             branches_by_named_id: HashMap::new(),
@@ -91,15 +103,11 @@ impl Treehouse {
         }
     }
 
-    pub fn report_diagnostics(&self) -> anyhow::Result<()> {
-        let writer = StandardStream::stderr(ColorChoice::Auto);
-        let config = codespan_reporting::term::Config::default();
-        for diagnostic in &self.diagnostics {
-            codespan_reporting::term::emit(&mut writer.lock(), &config, &self.files, diagnostic)
-                .context("could not emit diagnostic")?;
+    pub fn revision_info(&self, file_id: FileId) -> Option<&RevisionInfo> {
+        match self.source(file_id) {
+            Source::Tree { revision_info, .. } => Some(revision_info),
+            Source::Other(_) => None,
         }
-
-        Ok(())
     }
 
     pub fn next_missingno(&mut self) -> Ulid {
@@ -107,12 +115,6 @@ impl Treehouse {
             .generate()
             .expect("just how much disk space do you have?")
     }
-
-    pub fn has_errors(&self) -> bool {
-        self.diagnostics
-            .iter()
-            .any(|diagnostic| diagnostic.severity == Severity::Error)
-    }
 }
 
 pub struct TomlError {
@@ -140,3 +142,18 @@ pub fn toml_error_to_diagnostic(error: TomlError) -> Diagnostic<FileId> {
         notes: vec![],
     }
 }
+
+pub fn report_diagnostics(files: &Files, diagnostics: &[Diagnostic<FileId>]) -> anyhow::Result<()> {
+    let writer = StandardStream::stderr(ColorChoice::Auto);
+    let config = codespan_reporting::term::Config::default();
+    for diagnostic in diagnostics {
+        codespan_reporting::term::emit(&mut writer.lock(), &config, files, diagnostic)
+            .context("could not emit diagnostic")?;
+    }
+
+    Ok(())
+}
+
+pub fn has_errors(diagnostics: &[Diagnostic<FileId>]) -> bool {
+    diagnostics.iter().any(|d| d.severity == Severity::Error)
+}