backout: accept multiple revisions to back out

Closes #3339.

CHANGELOG.md

@@ -12,6 +12,9 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 * `jj rebase --skip-empty` has been renamed to `jj rebase --skip-emptied`
 
+* `jj backout --revision` has been renamed to `jj backout --revisions`.
+  The short alias `-r` is still supported.
+
 ### Deprecations
 
 ### New features
@@ -33,6 +36,8 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 * `jj backout` now includes the backed out commit's subject in the new commit
   message.
 
+* `jj backout` can now back out multiple commits at once.
+
 ### Fixed bugs
 
 ## [0.19.0] - 2024-07-03

cli/src/commands/backout.rs

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+use itertools::Itertools as _;
 use jj_lib::object_id::ObjectId;
 use jj_lib::rewrite::merge_commit_trees;
 use tracing::instrument;
@@ -23,9 +24,9 @@ use crate::ui::Ui;
 /// Apply the reverse of a revision on top of another revision
 #[derive(clap::Args, Clone, Debug)]
 pub(crate) struct BackoutArgs {
-    /// The revision to apply the reverse of
+    /// The revision(s) to apply the reverse of
     #[arg(long, short, default_value = "@")]
-    revision: RevisionArg,
+    revisions: Vec<RevisionArg>,
     /// The revision to apply the reverse changes on top of
     // TODO: It seems better to default this to `@-`. Maybe the working
     // copy should be rebased on top?
@@ -40,36 +41,54 @@ pub(crate) fn cmd_backout(
     args: &BackoutArgs,
 ) -> Result<(), CommandError> {
     let mut workspace_command = command.workspace_helper(ui)?;
-    let commit_to_back_out = workspace_command.resolve_single_rev(&args.revision)?;
+    let to_back_out: Vec<_> = workspace_command
+        .parse_union_revsets(&args.revisions)?
+        .evaluate_to_commits()?
+        .try_collect()?; // in reverse topological order
+    if to_back_out.is_empty() {
+        writeln!(ui.status(), "No revisions to back out.")?;
+        return Ok(());
+    }
     let mut parents = vec![];
     for revision_str in &args.destination {
         let destination = workspace_command.resolve_single_rev(revision_str)?;
         parents.push(destination);
     }
     let mut tx = workspace_command.start_transaction();
-    let commit_to_back_out_subject = commit_to_back_out
-        .description()
-        .lines()
-        .next()
-        .unwrap_or_default();
-    let new_commit_description = format!(
-        "Back out \"{}\"\n\nThis backs out commit {}.\n",
-        commit_to_back_out_subject,
-        &commit_to_back_out.id().hex()
-    );
-    let old_base_tree = commit_to_back_out.parent_tree(tx.mut_repo())?;
-    let new_base_tree = merge_commit_trees(tx.mut_repo(), &parents)?;
-    let old_tree = commit_to_back_out.tree()?;
-    let new_tree = new_base_tree.merge(&old_tree, &old_base_tree)?;
-    let new_parent_ids = parents.iter().map(|commit| commit.id().clone()).collect();
-    tx.mut_repo()
-        .new_commit(command.settings(), new_parent_ids, new_tree.id())
-        .set_description(new_commit_description)
-        .write()?;
-    tx.finish(
-        ui,
-        format!("back out commit {}", commit_to_back_out.id().hex()),
-    )?;
+    let transaction_description = if to_back_out.len() == 1 {
+        format!("back out commit {}", to_back_out[0].id().hex())
+    } else {
+        format!(
+            "back out commit {} and {} more",
+            to_back_out[0].id().hex(),
+            to_back_out.len() - 1
+        )
+    };
+    let mut new_base_tree = merge_commit_trees(tx.mut_repo(), &parents)?;
+    for commit_to_back_out in to_back_out {
+        let commit_to_back_out_subject = commit_to_back_out
+            .description()
+            .lines()
+            .next()
+            .unwrap_or_default();
+        let new_commit_description = format!(
+            "Back out \"{}\"\n\nThis backs out commit {}.\n",
+            commit_to_back_out_subject,
+            &commit_to_back_out.id().hex()
+        );
+        let old_base_tree = commit_to_back_out.parent_tree(tx.mut_repo())?;
+        let old_tree = commit_to_back_out.tree()?;
+        let new_tree = new_base_tree.merge(&old_tree, &old_base_tree)?;
+        let new_parent_ids = parents.iter().map(|commit| commit.id().clone()).collect();
+        let new_commit = tx
+            .mut_repo()
+            .new_commit(command.settings(), new_parent_ids, new_tree.id())
+            .set_description(new_commit_description)
+            .write()?;
+        parents = vec![new_commit];
+        new_base_tree = new_tree;
+    }
+    tx.finish(ui, transaction_description)?;
 
     Ok(())
 }

cli/tests/cli-reference@.md.snap

@@ -215,7 +215,7 @@ Apply the reverse of a revision on top of another revision
 
 ###### **Options:**
 
-* `-r`, `--revision <REVISION>` — The revision to apply the reverse of
+* `-r`, `--revisions <REVISIONS>` — The revision(s) to apply the reverse of
 
   Default value: `@`
 * `-d`, `--destination <DESTINATION>` — The revision to apply the reverse changes on top of

cli/tests/test_backout_command.rs

@@ -16,15 +16,23 @@ use std::path::Path;
 
 use crate::common::TestEnvironment;
 
-fn create_commit(test_env: &TestEnvironment, repo_path: &Path, name: &str, parents: &[&str]) {
+fn create_commit(
+    test_env: &TestEnvironment,
+    repo_path: &Path,
+    name: &str,
+    parents: &[&str],
+    files: &[(&str, &str)],
+) {
     if parents.is_empty() {
         test_env.jj_cmd_ok(repo_path, &["new", "root()", "-m", name]);
     } else {
         let mut args = vec!["new", "-m", name];
         args.extend(parents);
         test_env.jj_cmd_ok(repo_path, &args);
     }
-    std::fs::write(repo_path.join(name), format!("{name}\n")).unwrap();
+    for (name, contents) in files {
+        std::fs::write(repo_path.join(name), contents).unwrap();
+    }
     test_env.jj_cmd_ok(repo_path, &["branch", "create", name]);
 }
 
@@ -34,7 +42,7 @@ fn test_backout() {
     test_env.jj_cmd_ok(test_env.env_root(), &["init", "repo", "--git"]);
     let repo_path = test_env.env_root().join("repo");
 
-    create_commit(&test_env, &repo_path, "a", &[]);
+    create_commit(&test_env, &repo_path, "a", &[], &[("a", "a\n")]);
     // Test the setup
     insta::assert_snapshot!(get_log_output(&test_env, &repo_path), @r###"
     @  2443ea76b0b1 a
@@ -82,6 +90,104 @@ fn test_backout() {
     "###);
 }
 
+#[test]
+fn test_backout_multiple() {
+    let test_env = TestEnvironment::default();
+    test_env.jj_cmd_ok(test_env.env_root(), &["init", "repo", "--git"]);
+    let repo_path = test_env.env_root().join("repo");
+
+    create_commit(&test_env, &repo_path, "a", &[], &[("a", "a\n")]);
+    create_commit(&test_env, &repo_path, "b", &["a"], &[("a", "a\nb\n")]);
+    create_commit(
+        &test_env,
+        &repo_path,
+        "c",
+        &["b"],
+        &[("a", "a\nb\n"), ("b", "b\n")],
+    );
+    create_commit(&test_env, &repo_path, "d", &["c"], &[]);
+    create_commit(&test_env, &repo_path, "e", &["d"], &[("a", "a\nb\nc\n")]);
+
+    // Test the setup
+    insta::assert_snapshot!(get_log_output(&test_env, &repo_path), @r###"
+    @  208f8612074a e
+    ◉  ceeec03be46b d
+    ◉  413337bbd11f c
+    ◉  46cc97af6802 b
+    ◉  2443ea76b0b1 a
+    ◉  000000000000
+    "###);
+
+    // Backout multiple commits
+    let (stdout, stderr) =
+        test_env.jj_cmd_ok(&repo_path, &["backout", "-r", "b", "-r", "c", "-r", "e"]);
+    insta::assert_snapshot!(stdout, @"");
+    insta::assert_snapshot!(stderr, @"");
+    insta::assert_snapshot!(get_log_output(&test_env, &repo_path), @r###"
+    ◉  6504c4ded177 Back out "b"
+    │
+    │  This backs out commit 46cc97af6802301d8db381386e8485ff3ff24ae6.
+    ◉  d31d42e0267f Back out "c"
+    │
+    │  This backs out commit 413337bbd11f7a6636c010d9e196acf801d8df2f.
+    ◉  8ff3fbc2ccb0 Back out "e"
+    │
+    │  This backs out commit 208f8612074af4c219d06568a8e1f04f2e80dc25.
+    @  208f8612074a e
+    ◉  ceeec03be46b d
+    ◉  413337bbd11f c
+    ◉  46cc97af6802 b
+    ◉  2443ea76b0b1 a
+    ◉  000000000000
+    "###);
+    // View the output of each backed out commit
+    let stdout = test_env.jj_cmd_success(&repo_path, &["show", "@+"]);
+    insta::assert_snapshot!(stdout, @r###"
+    Commit ID: 8ff3fbc2ccb0d66985f558c461d1643cebb4c7d6
+    Change ID: wqnwkozpkustnxypnnntnykwrqrkrpvv
+    Author: Test User <[email protected]> (2001-02-03 08:05:19)
+    Committer: Test User <[email protected]> (2001-02-03 08:05:19)
+
+        Back out "e"
+
+        This backs out commit 208f8612074af4c219d06568a8e1f04f2e80dc25.
+
+    Modified regular file a:
+       1    1: a
+       2    2: b
+       3     : c
+    "###);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["show", "@++"]);
+    insta::assert_snapshot!(stdout, @r###"
+    Commit ID: d31d42e0267f6524d445348b1dd00926c62a6b57
+    Change ID: mouksmquosnpvwqrpsvvxtxpywpnxlss
+    Author: Test User <[email protected]> (2001-02-03 08:05:19)
+    Committer: Test User <[email protected]> (2001-02-03 08:05:19)
+
+        Back out "c"
+
+        This backs out commit 413337bbd11f7a6636c010d9e196acf801d8df2f.
+
+    Removed regular file b:
+       1     : b
+    "###);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["show", "@+++"]);
+    insta::assert_snapshot!(stdout, @r###"
+    Commit ID: 6504c4ded177fba2334f76683d1aa643700d5073
+    Change ID: tqvpomtpwrqsylrpsxknultrymmqxmxv
+    Author: Test User <[email protected]> (2001-02-03 08:05:19)
+    Committer: Test User <[email protected]> (2001-02-03 08:05:19)
+
+        Back out "b"
+
+        This backs out commit 46cc97af6802301d8db381386e8485ff3ff24ae6.
+
+    Modified regular file a:
+       1    1: a
+       2     : b
+    "###);
+}
+
 fn get_log_output(test_env: &TestEnvironment, cwd: &Path) -> String {
     let template = r#"commit_id.short() ++ " " ++ description"#;
     test_env.jj_cmd_success(cwd, &["log", "-T", template])