From 183f8414624eb37174344dc8849a56c619f0c9ae Mon Sep 17 00:00:00 2001
From: Benjamin Tan <benjamin@dev.ofcr.se>
Date: Fri, 26 Apr 2024 21:56:55 +0800
Subject: [PATCH] backout: add `--template` option

---
 cli/src/commands/backout.rs       |  27 ++++++++
 cli/src/config/templates.toml     |   2 +
 cli/tests/cli-reference@.md.snap  |   1 +
 cli/tests/runner.rs               |   1 +
 cli/tests/test_backout_command.rs | 102 ++++++++++++++++++++++++++++++
 lib/src/rewrite.rs                |   6 +-
 6 files changed, 138 insertions(+), 1 deletion(-)
 create mode 100644 cli/tests/test_backout_command.rs

diff --git a/cli/src/commands/backout.rs b/cli/src/commands/backout.rs
index 1538b848e5..a2cc011ac3 100644
--- a/cli/src/commands/backout.rs
+++ b/cli/src/commands/backout.rs
@@ -18,6 +18,8 @@ use tracing::instrument;
 
 use crate::cli_util::{CommandHelper, RevisionArg};
 use crate::command_error::CommandError;
+use crate::commit_templater::CommitTemplateLanguage;
+use crate::formatter::PlainTextFormatter;
 use crate::ui::Ui;
 
 /// Apply the reverse of a revision on top of another revision
@@ -31,6 +33,11 @@ pub(crate) struct BackoutArgs {
     // copy should be rebased on top?
     #[arg(long, short, default_value = "@")]
     destination: Vec<RevisionArg>,
+    /// Template used to generate the commit message
+    ///
+    /// For the syntax, see https://github.com/martinvonz/jj/blob/main/docs/templates.md
+    #[arg(long, short = 'T')]
+    template: Option<String>,
 }
 
 #[instrument(skip_all)]
@@ -47,11 +54,31 @@ pub(crate) fn cmd_backout(
         parents.push(destination);
     }
     let mut tx = workspace_command.start_transaction();
+    let commit_description = {
+        let language = tx.base_workspace_helper().commit_template_language()?;
+        let template_string = match &args.template {
+            Some(value) => value.to_string(),
+            None => command
+                .settings()
+                .config()
+                .get_string("templates.backout")?,
+        };
+        let template = tx.base_workspace_helper().parse_template(
+            &language,
+            &template_string,
+            CommitTemplateLanguage::wrap_commit,
+        )?;
+        let mut output = Vec::new();
+        let mut formatter = PlainTextFormatter::new(&mut output);
+        template.format(&commit_to_back_out, &mut formatter)?;
+        String::from_utf8(output).expect("template output should be utf-8 bytes")
+    };
     back_out_commit(
         command.settings(),
         tx.mut_repo(),
         &commit_to_back_out,
         &parents,
+        Some(commit_description),
     )?;
     tx.finish(
         ui,
diff --git a/cli/src/config/templates.toml b/cli/src/config/templates.toml
index f188f43b2e..706895ca2a 100644
--- a/cli/src/config/templates.toml
+++ b/cli/src/config/templates.toml
@@ -1,4 +1,6 @@
 [templates]
+backout = '"backout of commit " ++ commit_id'
+
 commit_summary = 'format_commit_summary_with_refs(self, branches)'
 commit_summary_no_branches = 'format_commit_summary_with_refs(self, "")'
 
diff --git a/cli/tests/cli-reference@.md.snap b/cli/tests/cli-reference@.md.snap
index 76bc688160..9f7ce7f550 100644
--- a/cli/tests/cli-reference@.md.snap
+++ b/cli/tests/cli-reference@.md.snap
@@ -217,6 +217,7 @@ Apply the reverse of a revision on top of another revision
 * `-d`, `--destination <DESTINATION>` — The revision to apply the reverse changes on top of
 
   Default value: `@`
+* `-T`, `--template <TEMPLATE>` — Template used to generate the commit message
 
 
 
diff --git a/cli/tests/runner.rs b/cli/tests/runner.rs
index 38134d8a0e..30c2572e48 100644
--- a/cli/tests/runner.rs
+++ b/cli/tests/runner.rs
@@ -11,6 +11,7 @@ fn test_no_forgotten_test_files() {
 mod test_abandon_command;
 mod test_advance_branches;
 mod test_alias;
+mod test_backout_command;
 mod test_branch_command;
 mod test_builtin_aliases;
 mod test_cat_command;
diff --git a/cli/tests/test_backout_command.rs b/cli/tests/test_backout_command.rs
new file mode 100644
index 0000000000..bc21ad909e
--- /dev/null
+++ b/cli/tests/test_backout_command.rs
@@ -0,0 +1,102 @@
+// Copyright 2024 The Jujutsu Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use std::path::Path;
+
+use crate::common::TestEnvironment;
+
+fn create_commit(test_env: &TestEnvironment, repo_path: &Path, name: &str, parents: &[&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();
+    test_env.jj_cmd_ok(repo_path, &["branch", "create", name]);
+}
+
+#[test]
+fn test_backout() {
+    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", &[]);
+    // Test the setup
+    insta::assert_snapshot!(get_log_output(&test_env, &repo_path), @r###"
+    @  2443ea76b0b1 a
+    ◉  000000000000
+    "###);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "-s"]);
+    insta::assert_snapshot!(stdout, @r###"
+    A a
+    "###);
+
+    let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["backout", "-r", "a"]);
+    insta::assert_snapshot!(stdout, @"");
+    insta::assert_snapshot!(stderr, @"");
+    insta::assert_snapshot!(get_log_output(&test_env, &repo_path), @r###"
+    ◉  8fe4e9345020 backout of commit 2443ea76b0b1c531326908326aab7020abab8e6c
+    @  2443ea76b0b1 a
+    ◉  000000000000
+    "###);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "-s", "-r", "@+"]);
+    insta::assert_snapshot!(stdout, @r###"
+    D a
+    "###);
+}
+
+#[test]
+fn test_backout_template() {
+    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", &[]);
+    // Test the setup
+    insta::assert_snapshot!(get_log_output(&test_env, &repo_path), @r###"
+    @  2443ea76b0b1 a
+    ◉  000000000000
+    "###);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "-s"]);
+    insta::assert_snapshot!(stdout, @r###"
+    A a
+    "###);
+
+    // Verify that message of backed out commit follows the provided template
+    let (stdout, stderr) = test_env.jj_cmd_ok(
+        &repo_path,
+        &[
+            "backout",
+            "-r",
+            "a",
+            "-T",
+            r#""Revert commit " ++ commit_id.short() ++ " \"" ++ description.first_line() ++ "\"""#,
+        ],
+    );
+    insta::assert_snapshot!(stdout, @"");
+    insta::assert_snapshot!(stderr, @"");
+    insta::assert_snapshot!(get_log_output(&test_env, &repo_path), @r###"
+    ◉  1db880a5204e Revert commit 2443ea76b0b1 "a"
+    @  2443ea76b0b1 a
+    ◉  000000000000
+    "###);
+}
+
+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])
+}
diff --git a/lib/src/rewrite.rs b/lib/src/rewrite.rs
index 6915cb5bd5..3bc77ce0fe 100644
--- a/lib/src/rewrite.rs
+++ b/lib/src/rewrite.rs
@@ -314,6 +314,7 @@ pub fn back_out_commit(
     mut_repo: &mut MutableRepo,
     old_commit: &Commit,
     new_parents: &[Commit],
+    commit_description: Option<String>,
 ) -> BackendResult<Commit> {
     let old_base_tree = merge_commit_trees(mut_repo, &old_commit.parents())?;
     let new_base_tree = merge_commit_trees(mut_repo, new_parents)?;
@@ -326,7 +327,10 @@ pub fn back_out_commit(
     // TODO: i18n the description based on repo language
     mut_repo
         .new_commit(settings, new_parent_ids, new_tree.id())
-        .set_description(format!("backout of commit {}", &old_commit.id().hex()))
+        .set_description(
+            commit_description
+                .unwrap_or_else(|| format!("backout of commit {}", &old_commit.id().hex())),
+        )
         .write()
 }