view: extract method that iterates local branches only

I'll probably reorganize the local/remote branches structure, so let's
minimize call sites which rely on the BranchTarget struct.

cli/src/commands/mod.rs

@@ -1610,12 +1610,14 @@ fn cmd_status(
         formatter.write_str("No working copy\n")?;
     }
 
-    let mut conflicted_local_branches = vec![];
+    let conflicted_local_branches = repo
+        .view()
+        .local_branches()
+        .filter(|(_, target)| target.has_conflict())
+        .map(|(branch_name, _)| branch_name)
+        .collect_vec();
     let mut conflicted_remote_branches = vec![];
     for (branch_name, branch_target) in repo.view().branches() {
-        if branch_target.local_target.has_conflict() {
-            conflicted_local_branches.push(branch_name.clone());
-        }
         for (remote_name, remote_target) in &branch_target.remote_targets {
             if remote_target.has_conflict() {
                 conflicted_remote_branches.push((branch_name.clone(), remote_name.clone()));

lib/src/git.rs

@@ -362,12 +362,8 @@ fn diff_refs_to_import(
 /// `view.git_refs()`. Main difference is that local branches can be moved by
 /// tracking remotes, and such mutation isn't applied to `view.git_refs()` yet.
 fn pinned_commit_ids(view: &View) -> impl Iterator<Item = &CommitId> {
-    let branch_ref_targets = view
-        .branches()
-        .values()
-        .map(|branch_target| &branch_target.local_target);
     itertools::chain!(
-        branch_ref_targets,
+        view.local_branches().map(|(_, target)| target),
         view.tags().values(),
         iter::once(view.git_head()),
     )
@@ -852,9 +848,7 @@ pub fn fetch(
     // help branch forget`.
     let nonempty_branches: HashSet<_> = mut_repo
         .view()
-        .branches()
-        .iter()
-        .filter(|&(_branch, target)| target.local_target.is_present())
+        .local_branches()
         .map(|(branch, _target)| branch.to_owned())
         .collect();
     // TODO: Inform the user if the export failed? In most cases, export is not

lib/src/repo.rs

@@ -872,9 +872,8 @@ impl MutableRepo {
         commit: &Commit,
     ) -> Result<(), EditCommitError> {
         fn local_branch_target_ids(view: &View) -> impl Iterator<Item = &CommitId> {
-            view.branches()
-                .values()
-                .flat_map(|branch_target| branch_target.local_target.added_ids())
+            view.local_branches()
+                .flat_map(|(_, target)| target.added_ids())
         }
 
         let maybe_wc_commit_id = self

lib/src/rewrite.rs

@@ -233,12 +233,12 @@ impl<'settings, 'repo> DescendantRebaser<'settings, 'repo> {
         // Build a map from commit to branches pointing to it, so we don't need to scan
         // all branches each time we rebase a commit.
         let mut branches: HashMap<_, HashSet<_>> = HashMap::new();
-        for (branch_name, branch_target) in mut_repo.view().branches() {
-            for commit in branch_target.local_target.added_ids() {
+        for (branch_name, target) in mut_repo.view().local_branches() {
+            for commit in target.added_ids() {
                 branches
                     .entry(commit.clone())
                     .or_default()
-                    .insert(branch_name.clone());
+                    .insert(branch_name.to_owned());
             }
         }
 

lib/src/view.rs

@@ -160,6 +160,15 @@ impl View {
         self.data.branches.remove(name);
     }
 
+    /// Iterates local branch `(name, target)`s in lexicographical order.
+    pub fn local_branches(&self) -> impl Iterator<Item = (&str, &RefTarget)> {
+        self.data
+            .branches
+            .iter()
+            .map(|(name, branch_target)| (name.as_ref(), &branch_target.local_target))
+            .filter(|(_, target)| target.is_present())
+    }
+
     pub fn get_local_branch(&self, name: &str) -> &RefTarget {
         if let Some(branch_target) = self.data.branches.get(name) {
             &branch_target.local_target