store: reduce duplication in Workspace and Repo init code

There is a bit of duplicated across the three functions for creating a
`Workspace` and `Repo`. This patch reduces that duplication by passing
in a closure.

In addition to reducing duplication, this is a step towards making it
easier to add new backends.

lib/src/repo.rs

@@ -23,12 +23,14 @@ use std::sync::{Arc, Mutex};
 use itertools::Itertools;
 use thiserror::Error;
 
-use crate::backend::{BackendError, ChangeId, CommitId};
+use crate::backend::{Backend, BackendError, ChangeId, CommitId};
 use crate::commit::Commit;
 use crate::commit_builder::CommitBuilder;
 use crate::dag_walk::topo_order_reverse;
+use crate::git_backend::GitBackend;
 use crate::index::{IndexRef, MutableIndex, ReadonlyIndex};
 use crate::index_store::IndexStore;
+use crate::local_backend::LocalBackend;
 use crate::op_heads_store::{LockedOpHeads, OpHeads, OpHeadsStore};
 use crate::op_store::{BranchTarget, OpStore, OperationId, RefTarget, WorkspaceId};
 use crate::operation::Operation;
@@ -127,18 +129,16 @@ impl Debug for ReadonlyRepo {
 
 impl ReadonlyRepo {
     pub fn init_local(settings: &UserSettings, repo_path: PathBuf) -> Arc<ReadonlyRepo> {
-        let repo_path = repo_path.canonicalize().unwrap();
-        ReadonlyRepo::init_repo_dir(&repo_path);
-        let store = Store::init_local(repo_path.join("store"));
-        ReadonlyRepo::init(settings, repo_path, store)
+        Self::init(settings, repo_path, |store_path| {
+            Box::new(LocalBackend::init(store_path))
+        })
     }
 
     /// Initializes a repo with a new Git backend in .jj/git/ (bare Git repo)
     pub fn init_internal_git(settings: &UserSettings, repo_path: PathBuf) -> Arc<ReadonlyRepo> {
-        let repo_path = repo_path.canonicalize().unwrap();
-        ReadonlyRepo::init_repo_dir(&repo_path);
-        let store = Store::init_internal_git(repo_path.join("store"));
-        ReadonlyRepo::init(settings, repo_path, store)
+        Self::init(settings, repo_path, |store_path| {
+            Box::new(GitBackend::init_internal(store_path))
+        })
     }
 
     /// Initializes a repo with an existing Git backend at the specified path
@@ -147,10 +147,9 @@ impl ReadonlyRepo {
         repo_path: PathBuf,
         git_repo_path: PathBuf,
     ) -> Arc<ReadonlyRepo> {
-        let repo_path = repo_path.canonicalize().unwrap();
-        ReadonlyRepo::init_repo_dir(&repo_path);
-        let store = Store::init_external_git(repo_path.join("store"), git_repo_path);
-        ReadonlyRepo::init(settings, repo_path, store)
+        Self::init(settings, repo_path, |store_path| {
+            Box::new(GitBackend::init_external(store_path, git_repo_path.clone()))
+        })
     }
 
     fn init_repo_dir(repo_path: &Path) {
@@ -160,15 +159,16 @@ impl ReadonlyRepo {
         fs::create_dir(repo_path.join("index")).unwrap();
     }
 
-    fn init(
+    pub fn init(
         user_settings: &UserSettings,
         repo_path: PathBuf,
-        store: Arc<Store>,
+        backend_factory: impl FnOnce(PathBuf) -> Box<dyn Backend>,
     ) -> Arc<ReadonlyRepo> {
+        let repo_path = repo_path.canonicalize().unwrap();
+        ReadonlyRepo::init_repo_dir(&repo_path);
+        let store = Store::new(backend_factory(repo_path.join("store")));
         let repo_settings = user_settings.with_repo(&repo_path).unwrap();
-
         let op_store: Arc<dyn OpStore> = Arc::new(SimpleOpStore::init(repo_path.join("op_store")));
-
         let mut root_view = op_store::View::default();
         root_view.head_ids.insert(store.root_commit_id().clone());
         root_view
@@ -177,11 +177,8 @@ impl ReadonlyRepo {
         let (op_heads_store, init_op) =
             OpHeadsStore::init(repo_path.join("op_heads"), &op_store, &root_view);
         let op_heads_store = Arc::new(op_heads_store);
-
         let index_store = Arc::new(IndexStore::init(repo_path.join("index")));
-
         let view = View::new(root_view);
-
         Arc::new(ReadonlyRepo {
             repo_path,
             store,

lib/src/store.rs

@@ -40,7 +40,7 @@ pub struct Store {
 }
 
 impl Store {
-    fn new(backend: Box<dyn Backend>) -> Arc<Self> {
+    pub fn new(backend: Box<dyn Backend>) -> Arc<Self> {
         let root_commit_id = CommitId::new(vec![0; backend.hash_length()]);
         Arc::new(Store {
             backend,
@@ -50,21 +50,6 @@ impl Store {
         })
     }
 
-    pub fn init_local(store_path: PathBuf) -> Arc<Self> {
-        Store::new(Box::new(LocalBackend::init(store_path)))
-    }
-
-    pub fn init_internal_git(store_path: PathBuf) -> Arc<Self> {
-        Store::new(Box::new(GitBackend::init_internal(store_path)))
-    }
-
-    pub fn init_external_git(store_path: PathBuf, git_repo_path: PathBuf) -> Arc<Self> {
-        Store::new(Box::new(GitBackend::init_external(
-            store_path,
-            git_repo_path,
-        )))
-    }
-
     pub fn load_store(store_path: PathBuf) -> Arc<Store> {
         let git_target_path = store_path.join("git_target");
         let backend: Box<dyn Backend> = if git_target_path.is_file() {

lib/src/testutils.rs

@@ -24,6 +24,8 @@ use tempfile::TempDir;
 use crate::backend::{FileId, TreeId, TreeValue};
 use crate::commit::Commit;
 use crate::commit_builder::CommitBuilder;
+use crate::git_backend::GitBackend;
+use crate::local_backend::LocalBackend;
 use crate::repo::{MutableRepo, ReadonlyRepo};
 use crate::repo_path::RepoPath;
 use crate::rewrite::RebasedDescendant;
@@ -68,9 +70,13 @@ impl TestRepo {
         let repo = if use_git {
             let git_path = temp_dir.path().join("git-repo");
             git2::Repository::init(&git_path).unwrap();
-            ReadonlyRepo::init_external_git(&settings, repo_dir, git_path)
+            ReadonlyRepo::init(&settings, repo_dir, |store_path| {
+                Box::new(GitBackend::init_external(store_path, git_path.clone()))
+            })
         } else {
-            ReadonlyRepo::init_local(&settings, repo_dir)
+            ReadonlyRepo::init(&settings, repo_dir, |store_path| {
+                Box::new(LocalBackend::init(store_path))
+            })
         };
 
         Self {

lib/src/workspace.rs

@@ -19,6 +19,9 @@ use std::sync::Arc;
 
 use thiserror::Error;
 
+use crate::backend::Backend;
+use crate::git_backend::GitBackend;
+use crate::local_backend::LocalBackend;
 use crate::op_store::WorkspaceId;
 use crate::repo::{ReadonlyRepo, RepoLoader};
 use crate::settings::UserSettings;
@@ -104,51 +107,39 @@ impl Workspace {
         user_settings: &UserSettings,
         workspace_root: PathBuf,
     ) -> Result<(Self, Arc<ReadonlyRepo>), WorkspaceInitError> {
-        let jj_dir = create_jj_dir(&workspace_root)?;
-        let repo_dir = jj_dir.join("repo");
-        std::fs::create_dir(&repo_dir).unwrap();
-        let repo = ReadonlyRepo::init_local(user_settings, repo_dir);
-        let (working_copy, repo) = init_working_copy(
-            user_settings,
-            &repo,
-            &workspace_root,
-            &jj_dir,
-            WorkspaceId::default(),
-        );
-        let repo_loader = repo.loader();
-        let workspace = Self::new(workspace_root, working_copy, repo_loader);
-        Ok((workspace, repo))
+        Self::init_with_backend(user_settings, workspace_root, |store_path| {
+            Box::new(LocalBackend::init(store_path))
+        })
     }
 
     pub fn init_internal_git(
         user_settings: &UserSettings,
         workspace_root: PathBuf,
     ) -> Result<(Self, Arc<ReadonlyRepo>), WorkspaceInitError> {
-        let jj_dir = create_jj_dir(&workspace_root)?;
-        let repo_dir = jj_dir.join("repo");
-        std::fs::create_dir(&repo_dir).unwrap();
-        let repo = ReadonlyRepo::init_internal_git(user_settings, repo_dir);
-        let (working_copy, repo) = init_working_copy(
-            user_settings,
-            &repo,
-            &workspace_root,
-            &jj_dir,
-            WorkspaceId::default(),
-        );
-        let repo_loader = repo.loader();
-        let workspace = Workspace::new(workspace_root, working_copy, repo_loader);
-        Ok((workspace, repo))
+        Self::init_with_backend(user_settings, workspace_root, |store_path| {
+            Box::new(GitBackend::init_internal(store_path))
+        })
     }
 
     pub fn init_external_git(
         user_settings: &UserSettings,
         workspace_root: PathBuf,
         git_repo_path: PathBuf,
+    ) -> Result<(Self, Arc<ReadonlyRepo>), WorkspaceInitError> {
+        Self::init_with_backend(user_settings, workspace_root, |store_path| {
+            Box::new(GitBackend::init_external(store_path, git_repo_path.clone()))
+        })
+    }
+
+    fn init_with_backend(
+        user_settings: &UserSettings,
+        workspace_root: PathBuf,
+        backend_factory: impl FnOnce(PathBuf) -> Box<dyn Backend>,
     ) -> Result<(Self, Arc<ReadonlyRepo>), WorkspaceInitError> {
         let jj_dir = create_jj_dir(&workspace_root)?;
         let repo_dir = jj_dir.join("repo");
         std::fs::create_dir(&repo_dir).unwrap();
-        let repo = ReadonlyRepo::init_external_git(user_settings, repo_dir, git_repo_path);
+        let repo = ReadonlyRepo::init(user_settings, repo_dir, backend_factory);
         let (working_copy, repo) = init_working_copy(
             user_settings,
             &repo,