Add a picker for jj bookmark list (#30883)

This PR adds a new picker for viewing a list of jj bookmarks, like you
would with `jj bookmark list`.

This is an exploration around what it would look like to begin adding
some dedicated jj features to Zed.

This is behind the `jj-ui` feature flag.

Release Notes:

- N/A

crates/jj/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "jj"
+version = "0.1.0"
+publish.workspace = true
+edition.workspace = true
+license = "GPL-3.0-or-later"
+
+[lints]
+workspace = true
+
+[lib]
+path = "src/jj.rs"
+
+[dependencies]
+anyhow.workspace = true
+gpui.workspace = true
+jj-lib.workspace = true
+workspace-hack.workspace = true

crates/jj/LICENSE-GPL

@@ -0,0 +1 @@
+../../LICENSE-GPL

crates/jj/src/jj.rs

@@ -0,0 +1,5 @@
+mod jj_repository;
+mod jj_store;
+
+pub use jj_repository::*;
+pub use jj_store::*;

crates/jj/src/jj_repository.rs

@@ -0,0 +1,72 @@
+use std::path::Path;
+use std::sync::Arc;
+
+use anyhow::Result;
+use gpui::SharedString;
+use jj_lib::config::StackedConfig;
+use jj_lib::repo::StoreFactories;
+use jj_lib::settings::UserSettings;
+use jj_lib::workspace::{self, DefaultWorkspaceLoaderFactory, WorkspaceLoaderFactory};
+
+#[derive(Debug, Clone)]
+pub struct Bookmark {
+    pub ref_name: SharedString,
+}
+
+pub trait JujutsuRepository: Send + Sync {
+    fn list_bookmarks(&self) -> Vec<Bookmark>;
+}
+
+pub struct RealJujutsuRepository {
+    repository: Arc<jj_lib::repo::ReadonlyRepo>,
+}
+
+impl RealJujutsuRepository {
+    pub fn new(cwd: &Path) -> Result<Self> {
+        let workspace_loader_factory = DefaultWorkspaceLoaderFactory;
+        let workspace_loader = workspace_loader_factory.create(Self::find_workspace_dir(cwd))?;
+
+        let config = StackedConfig::with_defaults();
+        let settings = UserSettings::from_config(config)?;
+
+        let workspace = workspace_loader.load(
+            &settings,
+            &StoreFactories::default(),
+            &workspace::default_working_copy_factories(),
+        )?;
+
+        let repo_loader = workspace.repo_loader();
+        let repository = repo_loader.load_at_head()?;
+
+        Ok(Self { repository })
+    }
+
+    fn find_workspace_dir(cwd: &Path) -> &Path {
+        cwd.ancestors()
+            .find(|path| path.join(".jj").is_dir())
+            .unwrap_or(cwd)
+    }
+}
+
+impl JujutsuRepository for RealJujutsuRepository {
+    fn list_bookmarks(&self) -> Vec<Bookmark> {
+        let bookmarks = self
+            .repository
+            .view()
+            .bookmarks()
+            .map(|(ref_name, _target)| Bookmark {
+                ref_name: ref_name.as_str().to_string().into(),
+            })
+            .collect();
+
+        bookmarks
+    }
+}
+
+pub struct FakeJujutsuRepository {}
+
+impl JujutsuRepository for FakeJujutsuRepository {
+    fn list_bookmarks(&self) -> Vec<Bookmark> {
+        Vec::new()
+    }
+}

crates/jj/src/jj_store.rs

@@ -0,0 +1,41 @@
+use std::path::Path;
+use std::sync::Arc;
+
+use gpui::{App, Entity, Global, prelude::*};
+
+use crate::{JujutsuRepository, RealJujutsuRepository};
+
+/// Note: We won't ultimately be storing the jj store in a global, we're just doing this for exploration purposes.
+struct GlobalJujutsuStore(Entity<JujutsuStore>);
+
+impl Global for GlobalJujutsuStore {}
+
+pub struct JujutsuStore {
+    repository: Arc<dyn JujutsuRepository>,
+}
+
+impl JujutsuStore {
+    pub fn init_global(cx: &mut App) {
+        let Some(repository) = RealJujutsuRepository::new(&Path::new(".")).ok() else {
+            return;
+        };
+
+        let repository = Arc::new(repository);
+        let jj_store = cx.new(|cx| JujutsuStore::new(repository, cx));
+
+        cx.set_global(GlobalJujutsuStore(jj_store));
+    }
+
+    pub fn try_global(cx: &App) -> Option<Entity<Self>> {
+        cx.try_global::<GlobalJujutsuStore>()
+            .map(|global| global.0.clone())
+    }
+
+    pub fn new(repository: Arc<dyn JujutsuRepository>, _cx: &mut Context<Self>) -> Self {
+        Self { repository }
+    }
+
+    pub fn repository(&self) -> &Arc<dyn JujutsuRepository> {
+        &self.repository
+    }
+}