Make change ids in tests repeatable

This will be needed to test functionality for showing shortest
unique prefix for commit and change ids. As a bonus, this also
allows us to test log output with change ids.

As another bonus, this will prevent occasional CI failures like
https://github.com/martinvonz/jj/actions/runs/3817554687/jobs/6493881468.

lib/src/commit_builder.rs

@@ -12,8 +12,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use uuid::Uuid;
-
 use crate::backend;
 use crate::backend::{BackendResult, ChangeId, CommitId, Signature, TreeId};
 use crate::commit::Commit;
@@ -28,10 +26,21 @@ pub struct CommitBuilder<'repo, 'settings> {
     rewrite_source: Option<Commit>,
 }
 
+#[cfg(test)]
 /// TODO: This function is still used in some tests, but shouldn't be. Its
-/// output is not reproducible. Its replacement is available in a follow-up commit.
+/// output is not reproducible.
 pub fn new_change_id_deprecated() -> ChangeId {
-    ChangeId::from_bytes(Uuid::new_v4().as_bytes())
+    ChangeId::from_bytes(uuid::Uuid::new_v4().as_bytes())
+}
+
+pub fn new_change_id(settings: &UserSettings) -> ChangeId {
+    let random_bytes = settings.random_gen();
+    // The `uuid` crate is used merely to specify the number of random bytes (16)
+    ChangeId::from_bytes(
+        uuid::Builder::from_random_bytes(random_bytes)
+            .into_uuid()
+            .as_bytes(),
+    )
 }
 
 impl CommitBuilder<'_, '_> {
@@ -47,7 +56,7 @@ impl CommitBuilder<'_, '_> {
             parents,
             predecessors: vec![],
             root_tree: tree_id,
-            change_id: new_change_id_deprecated(),
+            change_id: new_change_id(settings),
             description: String::new(),
             author: signature.clone(),
             committer: signature,
@@ -106,7 +115,7 @@ impl CommitBuilder<'_, '_> {
     }
 
     pub fn generate_new_change_id(mut self) -> Self {
-        self.commit.change_id = new_change_id_deprecated();
+        self.commit.change_id = new_change_id(self.settings);
         self
     }
 

tests/test_log_command.rs

@@ -61,6 +61,16 @@ fn test_log_with_or_without_diff() {
     o (no description set)
     "###);
 
+    // Test default log output format
+    insta::assert_snapshot!(test_env.jj_cmd_success(&repo_path, &["log"]), @r###"
+    @ ffdaa62087a2 [email protected] 2001-02-03 04:05:10.000 +07:00 789e536fd2e0
+    | a new commit
+    o 9a45c67d3e96 [email protected] 2001-02-03 04:05:08.000 +07:00 4291e264ae97
+    | add a file
+    o 000000000000  1970-01-01 00:00:00.000 +00:00 000000000000
+      (no description set)
+    "###);
+
     let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-T", "description", "--no-graph"]);
     insta::assert_snapshot!(stdout, @r###"
     a new commit