git: on implicit git export, use original view as source of git refs …

…(PoC)

(Partially?) fixes jj-vcs#922

lib/src/git.rs

@@ -26,7 +26,7 @@ use crate::git_backend::NO_GC_REF_NAMESPACE;
 use crate::op_store::RefTarget;
 use crate::repo::{MutableRepo, Repo};
 use crate::settings::GitSettings;
-use crate::view::RefName;
+use crate::view::{RefName, View};
 
 #[derive(Error, Debug, PartialEq)]
 pub enum GitImportError {
@@ -215,28 +215,37 @@ pub enum GitExportError {
     InternalGitError(#[from] git2::Error),
 }
 
+// XXX: clean up API, maybe update all callers to pass old_view = None?
+pub fn export_refs(
+    mut_repo: &mut MutableRepo,
+    git_repo: &git2::Repository,
+) -> Result<Vec<String>, GitExportError> {
+    export_refs2(mut_repo, git_repo, None)
+}
+
 /// Reflect changes made in the Jujutsu repo compared to our current view of the
 /// Git repo in `mut_repo.view().git_refs()`. Returns a list of names of
 /// branches that failed to export.
 // TODO: Also indicate why we failed to export these branches
-pub fn export_refs(
+pub fn export_refs2(
     mut_repo: &mut MutableRepo,
     git_repo: &git2::Repository,
+    maybe_old_view: Option<&View>,
 ) -> Result<Vec<String>, GitExportError> {
-    // First find the changes we want need to make without modifying mut_repo
     let mut branches_to_update = BTreeMap::new();
     let mut branches_to_delete = BTreeMap::new();
     let mut failed_branches = vec![];
-    let view = mut_repo.view();
-    let all_branch_names: HashSet<&str> = view
+    let old_view = maybe_old_view.unwrap_or(mut_repo.view());
+    let new_view = mut_repo.view();
+    let all_branch_names: HashSet<&str> = old_view
         .git_refs()
         .keys()
         .filter_map(|git_ref| git_ref.strip_prefix("refs/heads/"))
-        .chain(view.branches().keys().map(AsRef::as_ref))
+        .chain(new_view.branches().keys().map(AsRef::as_ref))
         .collect();
     for branch_name in all_branch_names {
-        let old_branch = view.get_git_ref(&format!("refs/heads/{branch_name}"));
-        let new_branch = view.get_local_branch(branch_name);
+        let old_branch = old_view.get_git_ref(&format!("refs/heads/{branch_name}"));
+        let new_branch = new_view.get_local_branch(branch_name);
         if new_branch == old_branch {
             continue;
         }

src/cli_util.rs

@@ -1073,8 +1073,10 @@ impl WorkspaceCommandHelper {
         }
         if self.working_copy_shared_with_git {
             self.export_head_to_git(mut_repo)?;
+            // Use the original view as the source of truth of the git repo.
+            let old_view = self.repo().view();
             let git_repo = self.repo.store().git_repo().unwrap();
-            let failed_branches = git::export_refs(mut_repo, &git_repo)?;
+            let failed_branches = git::export_refs2(mut_repo, &git_repo, Some(old_view))?;
             print_failed_git_export(ui, &failed_branches)?;
         }
         let maybe_old_commit = tx

tests/test_git_colocated.rs

@@ -287,13 +287,9 @@ fn test_git_colocated_squash_undo() {
     ◉  zzzzzzzzzzzz 000000000000
     "###);
     test_env.jj_cmd_success(&repo_path, &["undo"]);
-    // TODO: There should be no divergence here; 2f376ea1478c should be hidden
-    // (#922)
     insta::assert_snapshot!(get_log_output_divergence(&test_env, &repo_path), @r###"
-    ◉  qpvuntsmwlqt 2f376ea1478c A master !divergence!
-    │ @  rlvkpnrzqnoo 8f71e3b6a3be
-    │ ◉  qpvuntsmwlqt a86754f975f9 A !divergence!
-    ├─╯
+    @  rlvkpnrzqnoo 8f71e3b6a3be
+    ◉  qpvuntsmwlqt a86754f975f9 A master
     ◉  zzzzzzzzzzzz 000000000000
     "###);
 }