config: rename [alias] to [aliases], still supporting old name

The name of the [alias] section is inconsistent with other
table-valued sections ([revset-aliases], [colors], [merge-tools]), so
let's rename it. For comparison, `Cargo.toml` also uses plural names
(e.g. `[dependencies]`).

CHANGELOG.md

@@ -83,6 +83,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * `jj workspace root` prints the root path of the current workspace.
 
+* The `[alias]` config section was renamed to `[aliases]`. The old name is
+  still accepted for backwards compatibility for some time.
+
 ### Fixed bugs
 
 * When sharing the working copy with a Git repo, we used to forget to export

src/cli_util.rs

@@ -1718,7 +1718,18 @@ fn resolve_aliases(
     app: &Command,
     string_args: &[String],
 ) -> Result<Vec<String>, CommandError> {
-    let mut aliases_map = config.get_table("alias")?;
+    let mut aliases_map = config.get_table("aliases")?;
+    if let Ok(alias_map) = config.get_table("alias") {
+        for (alias, definition) in alias_map {
+            if aliases_map.insert(alias.clone(), definition).is_some() {
+                return Err(user_error_with_hint(
+                    format!(r#"Alias "{alias}" is defined in both [aliases] and [alias]"#),
+                    "[aliases] is the preferred section for aliases. Please remove the alias from \
+                     [alias].",
+                ));
+            }
+        }
+    }
     let mut resolved_aliases = HashSet::new();
     let mut string_args = string_args.to_vec();
     let mut real_commands = HashSet::new();

src/commands/config-schema.json

@@ -140,7 +140,7 @@
                 "type": "string"
             }
         },
-        "alias": {
+        "aliases": {
             "type": "object",
             "description": "Custom subcommand aliases to be supported by the jj command",
             "additionalProperties": {

src/config/misc.toml

@@ -1,4 +1,4 @@
-[alias]
+[aliases]
 # Placeholder: added by user
 
 [git]

tests/test_alias.rs

@@ -24,6 +24,22 @@ fn test_alias_basic() {
     test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
     let repo_path = test_env.env_root().join("repo");
 
+    test_env.add_config(r#"aliases.b = ["log", "-r", "@", "-T", "branches"]"#);
+    test_env.jj_cmd_success(&repo_path, &["branch", "create", "my-branch"]);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["b"]);
+    insta::assert_snapshot!(stdout, @r###"
+    @ my-branch
+    ~
+    "###);
+}
+
+#[test]
+fn test_alias_legacy_section() {
+    let test_env = TestEnvironment::default();
+    test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
+    let repo_path = test_env.env_root().join("repo");
+
+    // Can define aliases in [alias] section
     test_env.add_config(r#"alias.b = ["log", "-r", "@", "-T", "branches"]"#);
     test_env.jj_cmd_success(&repo_path, &["branch", "create", "my-branch"]);
     let stdout = test_env.jj_cmd_success(&repo_path, &["b"]);
@@ -31,6 +47,14 @@ fn test_alias_basic() {
     @ my-branch
     ~
     "###);
+
+    // The same alias (name) in both [alias] and [aliases] sections is an error
+    test_env.add_config(r#"aliases.b = ["branch", "list"]"#);
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["b"]);
+    insta::assert_snapshot!(stderr, @r###"
+    Error: Alias "b" is defined in both [aliases] and [alias]
+    Hint: [aliases] is the preferred section for aliases. Please remove the alias from [alias].
+    "###);
 }
 
 #[test]
@@ -55,7 +79,7 @@ fn test_alias_calls_unknown_command() {
     test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
     let repo_path = test_env.env_root().join("repo");
 
-    test_env.add_config(r#"alias.foo = ["nonexistent"]"#);
+    test_env.add_config(r#"aliases.foo = ["nonexistent"]"#);
     let stderr = test_env.jj_cmd_cli_error(&repo_path, &["foo"]);
     insta::assert_snapshot!(stderr, @r###"
     error: The subcommand 'nonexistent' wasn't recognized
@@ -72,7 +96,7 @@ fn test_alias_calls_command_with_invalid_option() {
     test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
     let repo_path = test_env.env_root().join("repo");
 
-    test_env.add_config(r#"alias.foo = ["log", "--nonexistent"]"#);
+    test_env.add_config(r#"aliases.foo = ["log", "--nonexistent"]"#);
     let stderr = test_env.jj_cmd_cli_error(&repo_path, &["foo"]);
     insta::assert_snapshot!(stderr, @r###"
     error: Found argument '--nonexistent' which wasn't expected, or isn't valid in this context
@@ -90,7 +114,7 @@ fn test_alias_calls_help() {
     let test_env = TestEnvironment::default();
     test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
     let repo_path = test_env.env_root().join("repo");
-    test_env.add_config(r#"alias.h = ["--help"]"#);
+    test_env.add_config(r#"aliases.h = ["--help"]"#);
     let stdout = test_env.jj_cmd_success(&repo_path, &["h"]);
     insta::assert_snapshot!(stdout.lines().take(5).join("\n"), @r###"
     Jujutsu (An experimental VCS)
@@ -107,7 +131,7 @@ fn test_alias_cannot_override_builtin() {
     test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
     let repo_path = test_env.env_root().join("repo");
 
-    test_env.add_config(r#"alias.log = ["rebase"]"#);
+    test_env.add_config(r#"aliases.log = ["rebase"]"#);
     // Alias should be ignored
     let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-r", "root"]);
     insta::assert_snapshot!(stdout, @r###"
@@ -123,7 +147,7 @@ fn test_alias_recursive() {
     let repo_path = test_env.env_root().join("repo");
 
     test_env.add_config(
-        r#"[alias]
+        r#"[aliases]
     foo = ["foo"]
     bar = ["baz"]
     baz = ["bar"]
@@ -146,7 +170,7 @@ fn test_alias_global_args_before_and_after() {
     let test_env = TestEnvironment::default();
     test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
     let repo_path = test_env.env_root().join("repo");
-    test_env.add_config(r#"alias.l = ["log", "-T", "commit_id", "-r", "all()"]"#);
+    test_env.add_config(r#"aliases.l = ["log", "-T", "commit_id", "-r", "all()"]"#);
     // Test the setup
     let stdout = test_env.jj_cmd_success(&repo_path, &["l"]);
     insta::assert_snapshot!(stdout, @r###"
@@ -182,7 +206,7 @@ fn test_alias_global_args_in_definition() {
     test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
     let repo_path = test_env.env_root().join("repo");
     test_env.add_config(
-        r#"alias.l = ["log", "-T", "commit_id", "--at-op", "@-", "-r", "all()", "--color=always"]"#,
+        r#"aliases.l = ["log", "-T", "commit_id", "--at-op", "@-", "-r", "all()", "--color=always"]"#,
     );
 
     // The global argument in the alias is respected
@@ -197,7 +221,7 @@ fn test_alias_invalid_definition() {
     let test_env = TestEnvironment::default();
 
     test_env.add_config(
-        r#"[alias]
+        r#"[aliases]
     non-list = 5
     non-string-list = [[]]
     "#,