cli: normalize line ending of edited commit description, ensure last newline

Since CR+LF vs LF things shouldn't matter in commit description, it's probably
better to normalize newline characters.

In Mercurial, ui.edit() and changelog.stripdesc() handle line normalization,
and trailing newlines are stripped. In Git, cleanup_message() handles that,
and the last newline is added after stripping trailing newlines.

src/cli_util.rs

@@ -1376,7 +1376,7 @@ impl AsRef<str> for DescriptionArg {
     }
 }
 
-fn complete_newline(s: &mut String) {
+pub fn complete_newline(s: &mut String) {
     if !s.is_empty() && !s.ends_with('\n') {
         s.push('\n');
     }

src/commands.rs

@@ -51,10 +51,10 @@ use maplit::{hashmap, hashset};
 use pest::Parser;
 
 use crate::cli_util::{
-    check_stale_working_copy, print_checkout_stats, print_failed_git_export, resolve_base_revs,
-    short_commit_description, short_commit_hash, user_error, user_error_with_hint,
-    write_commit_summary, Args, CommandError, CommandHelper, DescriptionArg, RevisionArg,
-    WorkspaceCommandHelper,
+    self, check_stale_working_copy, print_checkout_stats, print_failed_git_export,
+    resolve_base_revs, short_commit_description, short_commit_hash, user_error,
+    user_error_with_hint, write_commit_summary, Args, CommandError, CommandHelper, DescriptionArg,
+    RevisionArg, WorkspaceCommandHelper,
 };
 use crate::config::FullCommandArgs;
 use crate::diff_util::{self, DiffFormat, DiffFormatArgs};
@@ -1853,15 +1853,14 @@ fn edit_description(
     // Delete the file only if everything went well.
     // TODO: Tell the user the name of the file we left behind.
     std::fs::remove_file(description_file_path).ok();
-    let mut lines = description
-        .split_inclusive('\n')
+    // Normalize line ending, remove trailing blank lines.
+    let mut description = description
+        .lines()
         .filter(|line| !line.starts_with("JJ: "))
-        .collect_vec();
-    // Remove trailing blank lines
-    while matches!(lines.last(), Some(&"\n") | Some(&"\r\n")) {
-        lines.pop().unwrap();
-    }
-    Ok(lines.join(""))
+        .join("\n");
+    description.truncate(description.trim_end_matches('\n').len());
+    cli_util::complete_newline(&mut description);
+    Ok(description)
 }
 
 fn cmd_describe(

tests/test_commit_command.rs

@@ -55,8 +55,8 @@ modified",
     .unwrap();
     test_env.jj_cmd_success(&workspace_path, &["commit"]);
     insta::assert_snapshot!(get_log_output(&test_env, &workspace_path), @r###"
-    @ 3ea3453a773f (no description set)
-    o 792a60936c42 modified
+    @ 3df78bc2b9b5 (no description set)
+    o 30a8c2b3d6eb modified
     o 000000000000 (no description set)
     "###);
 }

tests/test_describe_command.rs

@@ -56,7 +56,7 @@ JJ: Lines starting with "JJ: " (like this one) will be removed.
     std::fs::write(&edit_script, "write\ndescription from editor").unwrap();
     let stdout = test_env.jj_cmd_success(&repo_path, &["describe"]);
     insta::assert_snapshot!(stdout, @r###"
-    Working copy now at: bfdd972f9349 description from editor
+    Working copy now at: 100943aeee3f description from editor
     "###);
 
     // Lines in editor starting with "JJ: " are ignored
@@ -70,6 +70,39 @@ JJ: Lines starting with "JJ: " (like this one) will be removed.
     Working copy now at: ccefa58bef47 description among comment
     "###);
 
+    // Multi-line description
+    std::fs::write(&edit_script, "write\nline1\nline2\n\nline4\n\n").unwrap();
+    let stdout = test_env.jj_cmd_success(&repo_path, &["describe"]);
+    insta::assert_snapshot!(stdout, @r###"
+    Working copy now at: e932ba42cef0 line1
+    "###);
+    let stdout =
+        test_env.jj_cmd_success(&repo_path, &["log", "--no-graph", "-r@", "-Tdescription"]);
+    insta::assert_snapshot!(stdout, @r###"
+    line1
+    line2
+
+    line4
+    "###);
+
+    // Multi-line description again with CRLF, which should make no changes
+    std::fs::write(&edit_script, "write\nline1\r\nline2\r\n\r\nline4\r\n\r\n").unwrap();
+    let stdout = test_env.jj_cmd_success(&repo_path, &["describe"]);
+    insta::assert_snapshot!(stdout, @r###"
+    Nothing changed.
+    "###);
+
+    // Clear description
+    let stdout = test_env.jj_cmd_success(&repo_path, &["describe", "-m", ""]);
+    insta::assert_snapshot!(stdout, @r###"
+    Working copy now at: d6957294acdc (no description set)
+    "###);
+    std::fs::write(&edit_script, "write\n").unwrap();
+    let stdout = test_env.jj_cmd_success(&repo_path, &["describe"]);
+    insta::assert_snapshot!(stdout, @r###"
+    Nothing changed.
+    "###);
+
     // Fails if the editor fails
     std::fs::write(&edit_script, "fail").unwrap();
     let stderr = test_env.jj_cmd_failure(&repo_path, &["describe"]);

tests/test_obslog_command.rs

@@ -136,7 +136,7 @@ fn test_obslog_squash() {
 
     let stdout = get_log_output(&test_env, &repo_path, &["obslog", "-p", "-r", "@-"]);
     insta::assert_snapshot!(stdout, @r###"
-    o    test.user@example.com 2001-02-03 04:05:10.000 +07:00 9b6d4a272a6a
+    o    test.user@example.com 2001-02-03 04:05:10.000 +07:00 27e721a5ba72
     |\  squashed
     | | Modified regular file file1:
     | |    1    1: foo