docs: update git compatibility docs for commit signing

It seems like a small usability improvement if users don't need to
enter the "$schema" link manually when they create a new config file.

This doesn't help existing users.

cli/tests/test_config_command.rs

@@ -231,6 +231,7 @@ fn test_config_list_layer() {
 
     let output = work_dir.run_jj(["config", "list", "--user"]);
     insta::assert_snapshot!(output, @r#"
+    "$schema" = "https://jj-vcs.github.io/jj/latest/config-schema.json"
     test-key = "test-val"
     test-layered-key = "test-original-val"
     [EOF]
@@ -255,6 +256,7 @@ fn test_config_list_layer() {
 
     let output = work_dir.run_jj(["config", "list", "--repo"]);
     insta::assert_snapshot!(output, @r#"
+    "$schema" = "https://jj-vcs.github.io/jj/latest/config-schema.json"
     test-layered-key = "test-layered-val"
     [EOF]
     "#);
@@ -304,6 +306,7 @@ fn test_config_list_origin() {
     ]);
     insta::assert_snapshot!(output, @r#"
     test-key = "test-val" # user $TEST_ENV/config/config.toml
+    "$schema" = "https://jj-vcs.github.io/jj/latest/config-schema.json" # repo $TEST_ENV/repo/.jj/repo/config.toml
     test-layered-key = "test-layered-val" # repo $TEST_ENV/repo/.jj/repo/config.toml
     user.name = "Test User" # env
     user.email = "test.user@example.com" # env
@@ -597,6 +600,7 @@ fn test_config_set_for_user() {
     let user_config_toml = std::fs::read_to_string(&user_config_path)
         .unwrap_or_else(|_| panic!("Failed to read file {}", user_config_path.display()));
     insta::assert_snapshot!(user_config_toml, @r#"
+    "$schema" = "https://jj-vcs.github.io/jj/latest/config-schema.json"
     test-key = "test-val"
 
     [test-table]
@@ -663,6 +667,7 @@ fn test_config_set_for_repo() {
     // Ensure test-key successfully written to user config.
     let repo_config_toml = work_dir.read_file(".jj/repo/config.toml");
     insta::assert_snapshot!(repo_config_toml, @r#"
+    "$schema" = "https://jj-vcs.github.io/jj/latest/config-schema.json"
     test-key = "test-val"
 
     [test-table]
@@ -691,6 +696,8 @@ fn test_config_set_toml_types() {
     set_value("test-table.string", r#""foo""#);
     set_value("test-table.invalid", r"a + b");
     insta::assert_snapshot!(std::fs::read_to_string(&user_config_path).unwrap(), @r#"
+    "$schema" = "https://jj-vcs.github.io/jj/latest/config-schema.json"
+
     [test-table]
     integer = 42
     float = 3.14
@@ -784,7 +791,10 @@ fn test_config_unset_inline_table_key() {
         .run_jj(["config", "unset", "--user", "inline-table.foo"])
         .success();
     let user_config_toml = std::fs::read_to_string(&user_config_path).unwrap();
-    insta::assert_snapshot!(user_config_toml, @"inline-table = {}");
+    insta::assert_snapshot!(user_config_toml, @r#"
+    "$schema" = "https://jj-vcs.github.io/jj/latest/config-schema.json"
+    inline-table = {}
+    "#);
 }
 
 #[test]
@@ -856,7 +866,11 @@ fn test_config_unset_for_user() {
         .success();
 
     let user_config_toml = std::fs::read_to_string(&user_config_path).unwrap();
-    insta::assert_snapshot!(user_config_toml, @"[table]");
+    insta::assert_snapshot!(user_config_toml, @r#"
+    "$schema" = "https://jj-vcs.github.io/jj/latest/config-schema.json"
+
+    [table]
+    "#);
 }
 
 #[test]
@@ -873,7 +887,7 @@ fn test_config_unset_for_repo() {
         .success();
 
     let repo_config_toml = work_dir.read_file(".jj/repo/config.toml");
-    insta::assert_snapshot!(repo_config_toml, @"");
+    insta::assert_snapshot!(repo_config_toml, @r#""$schema" = "https://jj-vcs.github.io/jj/latest/config-schema.json""#);
 }
 
 #[test]

docs/git-compatibility.md

@@ -68,9 +68,9 @@ a comparison with Git, including how workflows are different, see the
   copies backed by a single repo. See the `jj workspace` family of commands.
 * **Sparse checkouts: No.** However, there's native support for sparse
   checkouts. See the `jj sparse` command.
-* **Signed commits: Partial.**
+* **Signed commits: Yes.**
-  So far only [by configuration](https://github.com/jj-vcs/jj/blob/main/docs/config.md#commit-signing),
+  You can sign commits automatically [by configuration](https://github.com/jj-vcs/jj/blob/main/docs/config.md#commit-signing),
-  later perhaps [a command](https://github.com/jj-vcs/jj/pull/3142).
+  or use the `jj sign` command.
 * **Git LFS: No.** ([#80](https://github.com/jj-vcs/jj/issues/80))
 
 

lib/src/config.rs

@@ -559,11 +559,19 @@ impl ConfigFile {
             Err(ConfigLoadError::Read(PathError { path, error }))
                 if error.kind() == io::ErrorKind::NotFound =>
             {
-                Arc::new(ConfigLayer {
+                let mut data = DocumentMut::new();
+                data.insert(
+                    "$schema",
+                    toml_edit::Item::Value(
+                        "https://jj-vcs.github.io/jj/latest/config-schema.json".into(),
+                    ),
+                );
+                let layer = ConfigLayer {
                     source,
                     path: Some(path),
-                    data: DocumentMut::new(),
+                    data,
-                })
+                };
+                Arc::new(layer)
             }
             Err(err) => return Err(err),
         };