git: on initial export, export all branches

As I said in the previous patch, I don't know why I made the initial
export to Git a no-op. Exporting everything makes more sense to
(current-)me. It will make it slightly easier to skip exporting
conflicted branches (#463). It also lets us remove a `jj export` call
from `test_templater.rs`.

lib/src/git.rs

@@ -245,13 +245,16 @@ pub fn export_refs(
     upgrade_old_export_state(repo);
 
     let last_export_path = repo.repo_path().join("git_export_view");
-    if let Ok(mut last_export_file) = OpenOptions::new().read(true).open(&last_export_path) {
-        let thrift_view = simple_op_store::read_thrift(&mut last_export_file)
-            .map_err(|err| GitExportError::ReadStateError(err.to_string()))?;
-        let last_export_store_view = op_store::View::from(&thrift_view);
-        let last_export_view = View::new(last_export_store_view);
-        export_changes(&last_export_view, repo.view(), git_repo)?;
-    }
+    let last_export_store_view =
+        if let Ok(mut last_export_file) = OpenOptions::new().read(true).open(&last_export_path) {
+            let thrift_view = simple_op_store::read_thrift(&mut last_export_file)
+                .map_err(|err| GitExportError::ReadStateError(err.to_string()))?;
+            op_store::View::from(&thrift_view)
+        } else {
+            op_store::View::default()
+        };
+    let last_export_view = View::new(last_export_store_view);
+    export_changes(&last_export_view, repo.view(), git_repo)?;
     if let Ok(mut last_export_file) = OpenOptions::new()
         .write(true)
         .create(true)

lib/tests/test_git.rs

@@ -403,8 +403,9 @@ fn test_import_refs_detached_head() {
 }
 
 #[test]
-fn test_export_refs_initial() {
-    // The first export doesn't do anything
+fn test_export_refs_no_detach() {
+    // When exporting the branch that's current checked out, don't detach HEAD if
+    // the target already matches
     let mut test_data = GitRepoData::create();
     let git_repo = test_data.git_repo;
     let commit1 = empty_git_commit(&git_repo, "refs/heads/main", &[]);
@@ -416,7 +417,7 @@ fn test_export_refs_initial() {
         .unwrap();
     test_data.repo = tx.commit();
 
-    // The first export shouldn't do anything
+    // Do an initial export to make sure `main` is considered
     assert_eq!(git::export_refs(&test_data.repo, &git_repo), Ok(()));
     assert_eq!(git_repo.head().unwrap().name(), Some("refs/heads/main"));
     assert_eq!(

tests/test_templater.rs

@@ -27,8 +27,6 @@ fn test_templater_branches() {
         .join("repo")
         .join("store")
         .join("git");
-    // TODO: This initial export shouldn't be needed
-    test_env.jj_cmd_success(&origin_path, &["git", "export"]);
 
     // Created some branches on the remote
     test_env.jj_cmd_success(&origin_path, &["describe", "-m=description 1"]);
@@ -68,12 +66,12 @@ fn test_templater_branches() {
         &["log", "-T", r#"commit_id.short() " " branches"#],
     );
     insta::assert_snapshot!(output, @r###"
-    o 212985c08a44 branch3?
-    | @ cbf02da4e154 branch2* new-branch
-    | | o c794a4eab3b9 branch1*
+    o 48e0b6c42296 branch3?
+    | @ 092b2e0283a9 branch2* new-branch
+    | | o f4a739b1677f branch1*
     | |/  
     |/|   
-    | o 8cd8e5dc9595 branch2@origin
+    | o 752dad8b1718 branch2@origin
     |/  
     o 000000000000 
     "###);