cli: print commits abandoned by git::import_refs() or fetch()

This will probably help to understand why you've got conflicts after fetching.
Maybe we can also report changed local refs.

I think the stats should be redirected to stderr, but we have many other similar
messages printed to stdout. I'll probably fix them all at once later.

cli/src/cli_util.rs

@@ -34,7 +34,7 @@ use jj_lib::backend::{BackendError, ChangeId, CommitId, MergedTreeId, ObjectId};
 use jj_lib::commit::Commit;
 use jj_lib::git::{
     FailedRefExport, FailedRefExportReason, GitConfigParseError, GitExportError, GitImportError,
-    GitRemoteManagementError,
+    GitImportStats, GitRemoteManagementError,
 };
 use jj_lib::git_backend::GitBackend;
 use jj_lib::gitignore::GitIgnoreFile;
@@ -790,18 +790,18 @@ impl WorkspaceCommandHelper {
         ui: &mut Ui,
         git_repo: &Repository,
     ) -> Result<(), CommandError> {
-        let mut tx = self.start_transaction("import git refs").into_inner();
+        let git_settings = self.settings.git_settings();
+        let mut tx = self.start_transaction("import git refs");
         // Automated import shouldn't fail because of reserved remote name.
-        git::import_some_refs(
-            tx.mut_repo(),
-            git_repo,
-            &self.settings.git_settings(),
-            |ref_name| !git::is_reserved_git_remote_ref(ref_name),
-        )?;
+        let stats = git::import_some_refs(tx.mut_repo(), git_repo, &git_settings, |ref_name| {
+            !git::is_reserved_git_remote_ref(ref_name)
+        })?;
         if !tx.mut_repo().has_changes() {
             return Ok(());
         }
 
+        print_git_import_stats(ui, &tx, &stats)?;
+        let mut tx = tx.into_inner();
         let old_git_head = self.repo().view().git_head().clone();
         let new_git_head = tx.mut_repo().view().git_head().clone();
         // If the Git HEAD has changed, abandon our old checkout and check out the new
@@ -1797,6 +1797,26 @@ pub fn print_checkout_stats(ui: &mut Ui, stats: CheckoutStats) -> Result<(), std
     Ok(())
 }
 
+pub fn print_git_import_stats(
+    ui: &mut Ui,
+    tx: &WorkspaceCommandTransaction,
+    stats: &GitImportStats,
+) -> Result<(), CommandError> {
+    // TODO: maybe better to write status messages to stderr
+    if !stats.abandoned_commits.is_empty() {
+        ui.write("Abandoned the following commits:\n")?;
+        let store = tx.base_repo().store();
+        let helper = tx.base_workspace_helper();
+        for id in &stats.abandoned_commits {
+            ui.write("  ")?;
+            let commit = store.get_commit(id)?;
+            helper.write_commit_summary(ui.stdout_formatter().as_mut(), &commit)?;
+            ui.write("\n")?;
+        }
+    }
+    Ok(())
+}
+
 pub fn print_failed_git_export(
     ui: &Ui,
     failed_branches: &[FailedRefExport],

cli/src/commands/git.rs

@@ -26,9 +26,9 @@ use jj_lib::workspace::Workspace;
 use maplit::hashset;
 
 use crate::cli_util::{
-    print_failed_git_export, resolve_multiple_nonempty_revsets, short_change_hash,
-    short_commit_hash, user_error, user_error_with_hint, CommandError, CommandHelper, RevisionArg,
-    WorkspaceCommandHelper,
+    print_failed_git_export, print_git_import_stats, resolve_multiple_nonempty_revsets,
+    short_change_hash, short_commit_hash, user_error, user_error_with_hint, CommandError,
+    CommandHelper, RevisionArg, WorkspaceCommandHelper,
 };
 use crate::commands::make_branch_term;
 use crate::progress::Progress;
@@ -332,7 +332,7 @@ fn cmd_git_fetch(
     ));
     let branches = args.branch.iter().map(|b| b.as_str()).collect_vec();
     for remote in remotes {
-        with_remote_callbacks(ui, |cb| {
+        let stats = with_remote_callbacks(ui, |cb| {
             git::fetch(
                 tx.mut_repo(),
                 &git_repo,
@@ -347,6 +347,7 @@ fn cmd_git_fetch(
             GitFetchError::InternalGitError(err) => map_git_error(err),
             _ => user_error(err.to_string()),
         })?;
+        print_git_import_stats(ui, &tx, &stats.import_stats)?;
     }
     tx.finish(ui)?;
     Ok(())
@@ -547,6 +548,7 @@ fn do_git_clone(
             unreachable!("we didn't provide any globs")
         }
     })?;
+    print_git_import_stats(ui, &fetch_tx, &stats.import_stats)?;
     fetch_tx.finish(ui)?;
     Ok((workspace_command, git_repo, stats))
 }
@@ -977,7 +979,8 @@ fn cmd_git_push(
         ),
         _ => user_error(err.to_string()),
     })?;
-    git::import_refs(tx.mut_repo(), &git_repo, &command.settings().git_settings())?;
+    let stats = git::import_refs(tx.mut_repo(), &git_repo, &command.settings().git_settings())?;
+    print_git_import_stats(ui, &tx, &stats)?;
     tx.finish(ui)?;
     Ok(())
 }
@@ -1025,7 +1028,8 @@ fn cmd_git_import(
     let repo = workspace_command.repo();
     let git_repo = get_git_repo(repo.store())?;
     let mut tx = workspace_command.start_transaction("import git refs");
-    git::import_refs(tx.mut_repo(), &git_repo, &command.settings().git_settings())?;
+    let stats = git::import_refs(tx.mut_repo(), &git_repo, &command.settings().git_settings())?;
+    print_git_import_stats(ui, &tx, &stats)?;
     tx.finish(ui)?;
     Ok(())
 }

cli/src/commands/mod.rs

@@ -55,10 +55,10 @@ use tracing::instrument;
 
 use crate::cli_util::{
     self, check_stale_working_copy, get_new_config_file_path, print_checkout_stats,
-    resolve_multiple_nonempty_revsets, resolve_multiple_nonempty_revsets_default_single,
-    run_ui_editor, serialize_config_value, short_commit_hash, user_error, user_error_with_hint,
-    write_config_value_to_file, Args, CommandError, CommandHelper, LogContentFormat, RevisionArg,
-    WorkspaceCommandHelper,
+    print_git_import_stats, resolve_multiple_nonempty_revsets,
+    resolve_multiple_nonempty_revsets_default_single, run_ui_editor, serialize_config_value,
+    short_commit_hash, user_error, user_error_with_hint, write_config_value_to_file, Args,
+    CommandError, CommandHelper, LogContentFormat, RevisionArg, WorkspaceCommandHelper,
 };
 use crate::config::{AnnotatedValue, ConfigSource};
 use crate::diff_util::{self, DiffFormat, DiffFormatArgs};
@@ -1213,12 +1213,13 @@ fn cmd_init(ui: &mut Ui, command: &CommandHelper, args: &InitArgs) -> Result<(),
             git::add_to_git_exclude(ui, &git_repo)?;
         } else {
             let mut tx = workspace_command.start_transaction("import git refs");
-            jj_lib::git::import_some_refs(
+            let stats = jj_lib::git::import_some_refs(
                 tx.mut_repo(),
                 &git_repo,
                 &command.settings().git_settings(),
                 |ref_name| !jj_lib::git::is_reserved_git_remote_ref(ref_name),
             )?;
+            print_git_import_stats(ui, &tx, &stats)?;
             if let Some(git_head_id) = tx.mut_repo().view().git_head().as_normal().cloned() {
                 let git_head_commit = tx.mut_repo().store().get_commit(&git_head_id)?;
                 tx.check_out(&git_head_commit)?;

cli/tests/test_git_colocated.rs

@@ -158,6 +158,8 @@ fn test_git_colocated_rebase_on_import() {
     git_repo.branch("master", &commit1, true).unwrap();
     git_repo.set_head("refs/heads/master").unwrap();
     insta::assert_snapshot!(get_log_output(&test_env, &workspace_root), @r###"
+    Abandoned the following commits:
+      rlvkpnrz 45fbe1af master | modify a file
     @  7f96185cfbe36341d0f9a86ebfaeab67a5922c7e
     ◉  4bcbeaba9a4b309c5f45a8807fbf5499b9714315 master HEAD@git add a file
     ◉  0000000000000000000000000000000000000000
@@ -206,6 +208,8 @@ fn test_git_colocated_branches() {
         )
         .unwrap();
     insta::assert_snapshot!(get_log_output(&test_env, &workspace_root), @r###"
+    Abandoned the following commits:
+      kkmpptxz 35605592 master | (empty) bar
     Working copy now at: yqosqzyt 096dc80d (empty) (no description set)
     Parent commit      : qpvuntsm 230dd059 (empty) (no description set)
     @  096dc80da67094fbaa6683e2a205dddffa31f9a8
@@ -294,7 +298,11 @@ fn test_git_colocated_fetch_deleted_or_moved_branch() {
     // Move branch C sideways
     test_env.jj_cmd_success(&origin_path, &["describe", "C_to_move", "-m", "moved C"]);
     let stdout = test_env.jj_cmd_success(&clone_path, &["git", "fetch"]);
-    insta::assert_snapshot!(stdout, @"");
+    insta::assert_snapshot!(stdout, @r###"
+    Abandoned the following commits:
+      vnotlzrn 8d4e006f C_to_move | (empty) original C
+      wvpolxwl 929e298a B_to_delete | (empty) B_to_delete
+    "###);
     // "original C" and "B_to_delete" are abandoned, as the corresponding branches
     // were deleted or moved on the remote (#864)
     insta::assert_snapshot!(get_log_output(&test_env, &clone_path), @r###"

cli/tests/test_git_fetch.rs

@@ -474,7 +474,11 @@ fn test_git_fetch_all() {
     master: zowqyktl ff36dc55 descr_for_trunk1
     trunk1: zowqyktl ff36dc55 descr_for_trunk1
     "###);
-    insta::assert_snapshot!(test_env.jj_cmd_success(&target_jj_repo_path, &["git", "fetch"]), @"");
+    insta::assert_snapshot!(test_env.jj_cmd_success(&target_jj_repo_path, &["git", "fetch"]), @r###"
+    Abandoned the following commits:
+      qkvnknrk decaa396 a2 | descr_for_a2
+      nknoxmzm 359a9a02 a1 | descr_for_a1
+    "###);
     insta::assert_snapshot!(get_branch_output(&test_env, &target_jj_repo_path), @r###"
     a1: quxllqov 0424f6df descr_for_a1
     a2: osusxwst 91e46b4b descr_for_a2
@@ -625,7 +629,10 @@ fn test_git_fetch_some_of_many_branches() {
         &target_jj_repo_path,
         &["git", "fetch", "--branch", "b", "--branch", "a1"],
     );
-    insta::assert_snapshot!(stdout, @"");
+    insta::assert_snapshot!(stdout, @r###"
+    Abandoned the following commits:
+      nknoxmzm 359a9a02 a1 | descr_for_a1
+    "###);
     insta::assert_snapshot!(get_log_output(&test_env, &target_jj_repo_path), @r###"
     ◉  13ac032802f1 descr_for_b b?? b@origin
     │ ◉  6f4e1c4dfe29 descr_for_a1 a1
@@ -657,7 +664,10 @@ fn test_git_fetch_some_of_many_branches() {
         &target_jj_repo_path,
         &["git", "fetch", "--branch", "b", "--branch", "a*"],
     );
-    insta::assert_snapshot!(stdout, @"");
+    insta::assert_snapshot!(stdout, @r###"
+    Abandoned the following commits:
+      qkvnknrk decaa396 a2 | descr_for_a2
+    "###);
     insta::assert_snapshot!(get_log_output(&test_env, &target_jj_repo_path), @r###"
     ◉  010977d69c5b descr_for_a2 a2
     │ ◉  13ac032802f1 descr_for_b b?? b@origin
@@ -979,7 +989,10 @@ fn test_git_fetch_removed_branch() {
 
     // Fetch branches a2 from origin, and check that it has been removed locally
     let stdout = test_env.jj_cmd_success(&target_jj_repo_path, &["git", "fetch", "--branch", "a2"]);
-    insta::assert_snapshot!(stdout, @"");
+    insta::assert_snapshot!(stdout, @r###"
+    Abandoned the following commits:
+      qkvnknrk decaa396 a2 | descr_for_a2
+    "###);
     insta::assert_snapshot!(get_log_output(&test_env, &target_jj_repo_path), @r###"
     ◉  c7d4bdcbc215 descr_for_b b
     │ ◉  359a9a02457d descr_for_a1 a1
@@ -1046,7 +1059,10 @@ fn test_git_fetch_removed_parent_branch() {
             "git", "fetch", "--branch", "master", "--branch", "trunk1", "--branch", "a1",
         ],
     );
-    insta::assert_snapshot!(stdout, @"");
+    insta::assert_snapshot!(stdout, @r###"
+    Abandoned the following commits:
+      nknoxmzm 359a9a02 a1 | descr_for_a1
+    "###);
     insta::assert_snapshot!(get_log_output(&test_env, &target_jj_repo_path), @r###"
     ◉  c7d4bdcbc215 descr_for_b b
     │ ◉  decaa3966c83 descr_for_a2 a2

cli/tests/test_git_push.rs

@@ -295,6 +295,9 @@ fn test_git_push_multiple() {
       Delete branch branch1 from 45a3aa29e907
       Force branch branch2 from 8476341eb395 to 15dcdaa4f12f
       Add branch my-branch to 15dcdaa4f12f
+    Abandoned the following commits:
+      rlzusymt 8476341e branch2@origin | (empty) description 2
+      lzmmnrxq 45a3aa29 branch1@origin | (empty) description 1
     "###);
     let stdout = test_env.jj_cmd_success(&workspace_root, &["branch", "list"]);
     insta::assert_snapshot!(stdout, @r###"
@@ -571,6 +574,8 @@ fn test_git_push_deleted() {
     insta::assert_snapshot!(stdout, @r###"
     Branch changes to push to origin:
       Delete branch branch1 from 45a3aa29e907
+    Abandoned the following commits:
+      lzmmnrxq 45a3aa29 branch1@origin | (empty) description 1
     "###);
     let stdout = test_env.jj_cmd_success(&workspace_root, &["git", "push", "--deleted"]);
     insta::assert_snapshot!(stdout, @r###"