cli: add support for setting default description

That is, jj will use ui.default_description as a starting point when
user is about to describe an empty change.

I think it might be confusing to do this with -m / --stdin (violates
WYSIWYG), so I'm only doing this when jj invokes an editor.

Also, this could evolve into a proper template in the future instead of
just plain text, to allow inheriting from parent change(s), for example.

Partially addresses #1354.

CHANGELOG.md

@@ -59,11 +59,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   `-m/--message` arguments. Each passed message will be combined into paragraphs
   (separated by a blank line)
 
+* It is now possible to set a default description using the new
+  `ui.default-description` option, to use when describing changes with an empty
+  description.
+
 ### Fixed bugs
 
 * SSH authentication could hang when ssh-agent couldn't be reached
   [#1970](https://github.com/martinvonz/jj/issues/1970)
-  
+
 * SSH authentication can now use ed25519 and ed25519-sk keys. They still need
   to be password-less.
 

cli/src/commands/mod.rs

@@ -2015,7 +2015,7 @@ fn cmd_describe(
     } else if args.no_edit {
         commit.description().to_owned()
     } else {
-        let template = description_template_for_commit(ui, &workspace_command, &commit)?;
+        let template = description_template_for_commit(ui, command, &workspace_command, &commit)?;
         edit_description(workspace_command.repo(), &template, command.settings())?
     };
     if description == *commit.description() && !args.reset_author {
@@ -2048,7 +2048,7 @@ fn cmd_commit(ui: &mut Ui, command: &CommandHelper, args: &CommitArgs) -> Result
     let description = if !args.message_paragraphs.is_empty() {
         cli_util::join_message_paragraphs(&args.message_paragraphs)
     } else {
-        let template = description_template_for_commit(ui, &workspace_command, &commit)?;
+        let template = description_template_for_commit(ui, command, &workspace_command, &commit)?;
         edit_description(workspace_command.repo(), &template, command.settings())?
     };
 
@@ -2991,6 +2991,7 @@ don't make any changes, then the operation will be aborted.",
 
 fn description_template_for_commit(
     ui: &Ui,
+    command: &CommandHelper,
     workspace_command: &WorkspaceCommandHelper,
     commit: &Commit,
 ) -> Result<String, CommandError> {
@@ -3003,12 +3004,19 @@ fn description_template_for_commit(
         &EverythingMatcher,
         &[DiffFormat::Summary],
     )?;
-    if diff_summary_bytes.is_empty() {
-        Ok(commit.description().to_owned())
+    let description = if commit.description().is_empty() {
+        command
+            .settings()
+            .config()
+            .get_string("ui.default-description")
+            .unwrap_or("".to_owned())
     } else {
-        Ok(commit.description().to_owned()
-            + "\n"
-            + &diff_summary_to_description(&diff_summary_bytes))
+        commit.description().to_owned()
+    };
+    if diff_summary_bytes.is_empty() {
+        Ok(description)
+    } else {
+        Ok(description + "\n" + &diff_summary_to_description(&diff_summary_bytes))
     }
 }
 

cli/src/config-schema.json

@@ -46,6 +46,11 @@
                     "description": "Default command to run when no explicit command is given",
                     "default": "log"
                 },
+                "default-description": {
+                    "type": "string",
+                    "description": "Default description to use when describing changes with an empty description",
+                    "default": ""
+                },
                 "color": {
                     "description": "Whether to colorize command output",
                     "enum": [
@@ -62,7 +67,7 @@
                         "never",
                         "auto"
                     ],
-                     "default": "auto"
+                    "default": "auto"
                 },
                 "pager": {
                     "type": "string",

cli/tests/test_commit_command.rs

@@ -75,6 +75,38 @@ fn test_commit_with_editor() {
     "###);
 }
 
+#[test]
+fn test_commit_with_default_description() {
+    let mut test_env = TestEnvironment::default();
+    test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
+    test_env.add_config(r#"ui.default-description = "\n\nTESTED=TODO""#);
+    let workspace_path = test_env.env_root().join("repo");
+
+    std::fs::write(workspace_path.join("file1"), "foo\n").unwrap();
+    std::fs::write(workspace_path.join("file2"), "bar\n").unwrap();
+    let edit_script = test_env.set_up_fake_editor();
+    std::fs::write(&edit_script, ["dump editor"].join("\0")).unwrap();
+    test_env.jj_cmd_success(&workspace_path, &["commit"]);
+
+    insta::assert_snapshot!(get_log_output(&test_env, &workspace_path), @r#"
+    @  8dc0591d00f7
+    ◉  7e780ba80aeb TESTED=TODO
+    ◉  000000000000
+    "#);
+    assert_eq!(
+        std::fs::read_to_string(test_env.env_root().join("editor")).unwrap(),
+        r#"
+
+TESTED=TODO
+JJ: This commit contains the following changes:
+JJ:     A file1
+JJ:     A file2
+
+JJ: Lines starting with "JJ: " (like this one) will be removed.
+"#
+    );
+}
+
 #[test]
 fn test_commit_without_working_copy() {
     let test_env = TestEnvironment::default();

cli/tests/test_describe_command.rs

@@ -234,6 +234,37 @@ fn test_multiple_message_args() {
     "###);
 }
 
+#[test]
+fn test_describe_default_description() {
+    let mut test_env = TestEnvironment::default();
+    test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
+    test_env.add_config(r#"ui.default-description = "\n\nTESTED=TODO""#);
+    let workspace_path = test_env.env_root().join("repo");
+
+    std::fs::write(workspace_path.join("file1"), "foo\n").unwrap();
+    std::fs::write(workspace_path.join("file2"), "bar\n").unwrap();
+    let edit_script = test_env.set_up_fake_editor();
+    std::fs::write(&edit_script, ["dump editor"].join("\0")).unwrap();
+    let stdout = test_env.jj_cmd_success(&workspace_path, &["describe"]);
+
+    insta::assert_snapshot!(stdout, @r#"
+    Working copy now at: qpvuntsm 7e780ba8 TESTED=TODO
+    Parent commit      : zzzzzzzz 00000000 (empty) (no description set)
+    "#);
+    assert_eq!(
+        std::fs::read_to_string(test_env.env_root().join("editor")).unwrap(),
+        r#"
+
+TESTED=TODO
+JJ: This commit contains the following changes:
+JJ:     A file1
+JJ:     A file2
+
+JJ: Lines starting with "JJ: " (like this one) will be removed.
+"#
+    );
+}
+
 #[test]
 fn test_describe_author() {
     let test_env = TestEnvironment::default();

docs/config.md

@@ -135,6 +135,16 @@ subcommand name, subcommand alias, or user-defined alias (defaults to `"log"`).
 ui.default-command = "log"
 ```
 
+### Default description
+
+The value of the `ui.default-description` setting will be used to prepopulate
+the editor when describing changes with an empty description. This could be a
+useful reminder to fill in things like BUG=, TESTED= etc.
+
+```toml
+ui.default-description = "\n\nTESTED=TODO"
+```
+
 ### Diff format
 
 ```toml
@@ -179,13 +189,13 @@ revsets.log = "main.."
 
 ```toml
 # Possible values: "curved" (default), "square", "ascii", "ascii-large",
-# "legacy" 
+# "legacy"
 ui.graph.style = "square"
 ```
 
 ### Wrap log content
 
-If enabled, `log`/`obslog`/`op log` content will be wrapped based on 
+If enabled, `log`/`obslog`/`op log` content will be wrapped based on
 the terminal width.
 
 ```toml
@@ -274,7 +284,7 @@ a `$`):
 Additionally, paging behavior can be toggled via `ui.paginate` like so:
 
 ```toml
-# Enable pagination for commands that support it (default) 
+# Enable pagination for commands that support it (default)
 ui.paginate = "auto"
 # Disable all pagination, equivalent to using --no-pager
 ui.paginate = "never"