conflicts: use non-legacy MergedTreeId for root commit

This is part of migrating away from legacy trees (with path-level
conflicts). I can't think of any practical impact (we already compare
the tree ids equal).

cli/tests/test_util_command.rs

@@ -91,7 +91,7 @@ fn test_gc_operation_log() {
     // Now this doesn't work.
     let stderr = test_env.jj_cmd_failure(&repo_path, &["debug", "operation", &op_to_remove]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: No operation ID matching "1708ccd0d25f313f1559dfd1c4d16f0424de23a58e946830b0f27eb1252ce9295fe018e03fa4356e6aa39520cd8b5d44b7688024428988fe4d015291a4706172"
+    Error: No operation ID matching "54c5f04ab3dbb32ac86f805c819cb1ef78a3c9758ee560680a465e843fa0b05f42706d0641805905ef4bab550ca805effd1ba73d1980f6cdcc42126f008e51f4"
     "###);
 }
 

cli/tests/test_workspaces.rs

@@ -491,14 +491,14 @@ fn test_workspaces_current_op_discarded_by_other() {
         ],
     );
     insta::assert_snapshot!(stdout, @r###"
-    @  8e5ea0fbda abandon commit 3540d386892997a2a927078635a2d933e37499fb8691938a2f540c25bccffd9e8a60b2d5a8cb94bb3eeab17e1c56f96aafa2bcb66fa1e4eb96911d093d7a579e
-    ○  f336f5b6e8 Create initial working-copy commit in workspace secondary
-    ○  aacb3bda7d add workspace 'secondary'
-    ○  46bcf7d75e new empty commit
-    ○  4d2f5d7cbf snapshot working copy
-    ○  2f863a1573 new empty commit
-    ○  f01631d976 snapshot working copy
-    ○  17dbb2fe40 add workspace 'default'
+    @  dc722e2b8c abandon commit 20dd439c4bd12c6ad56c187ac490bd0141804618f638dc5c4dc92ff9aecba20f152b23160db9dcf61beb31a5cb14091d9def5a36d11c9599cc4d2e5689236af1
+    ○  2ddeb5e3b9 Create initial working-copy commit in workspace secondary
+    ○  0f99641958 add workspace 'secondary'
+    ○  5641361f60 new empty commit
+    ○  3a6c319c59 snapshot working copy
+    ○  42c6005842 new empty commit
+    ○  6a45045541 snapshot working copy
+    ○  a9e6630bf0 add workspace 'default'
     ○  cecfee9647 initialize repo
     ○  0000000000
     "###);
@@ -508,10 +508,10 @@ fn test_workspaces_current_op_discarded_by_other() {
     test_env.jj_cmd_ok(&main_path, &["util", "gc", "--expire=now"]);
 
     insta::assert_snapshot!(get_log_output(&test_env, &main_path), @r###"
-    @  cc0b087cb874 default@
-    │ ○  376eee1462a7 secondary@
+    ○  96b31dafdc41 secondary@
+    │ @  6c051bd1ccd5 default@
     ├─╯
-    ○  7788883a847c
+    ○  7c5b25a4fc8f
     ◆  000000000000
     "###);
 
@@ -524,17 +524,17 @@ fn test_workspaces_current_op_discarded_by_other() {
 
     let (stdout, stderr) = test_env.jj_cmd_ok(&secondary_path, &["workspace", "update-stale"]);
     insta::assert_snapshot!(stderr, @r###"
-    Failed to read working copy's current operation; attempting recovery. Error message from read attempt: Object f336f5b6e83bb901dce6d05d83193f7d0cad2b6375a9910d586c844a479feb130c30d417bdf3030f980d9bacca117584a654e9bdf74b41b30021651e28fbfc8c of type operation not found
-    Created and checked out recovery commit 6803354995e6
+    Failed to read working copy's current operation; attempting recovery. Error message from read attempt: Object 2ddeb5e3b9352cf199f29c30f0434a939723e710ec6247babc4a712718a6a9711cca54b083d9baff14c625800729248eb86f1766bca57573183a6f08ce735505 of type operation not found
+    Created and checked out recovery commit 62f70695e3b0
     "###);
     insta::assert_snapshot!(stdout, @"");
 
     insta::assert_snapshot!(get_log_output(&test_env, &main_path), @r###"
-    ○  a8f7db7868c1 secondary@
-    ○  376eee1462a7
-    │ @  cc0b087cb874 default@
+    ○  b0b400439a82 secondary@
+    ○  96b31dafdc41
+    │ @  6c051bd1ccd5 default@
     ├─╯
-    ○  7788883a847c
+    ○  7c5b25a4fc8f
     ◆  000000000000
     "###);
 
@@ -552,8 +552,8 @@ fn test_workspaces_current_op_discarded_by_other() {
     A added
     D deleted
     M modified
-    Working copy : kmkuslsw a8f7db78 (no description set)
-    Parent commit: rzvqmyuk 376eee14 (empty) (no description set)
+    Working copy : kmkuslsw b0b40043 (no description set)
+    Parent commit: rzvqmyuk 96b31daf (empty) (no description set)
     "###);
     // The modified file should have the same contents it had before (not reset to
     // the base contents)
@@ -564,9 +564,9 @@ fn test_workspaces_current_op_discarded_by_other() {
     let (stdout, stderr) = test_env.jj_cmd_ok(&secondary_path, &["obslog"]);
     insta::assert_snapshot!(stderr, @"");
     insta::assert_snapshot!(stdout, @r###"
-    @  kmkuslsw [email protected] 2001-02-03 08:05:18 secondary@ a8f7db78
+    @  kmkuslsw [email protected] 2001-02-03 08:05:18 secondary@ b0b40043
     │  (no description set)
-    ○  kmkuslsw hidden [email protected] 2001-02-03 08:05:18 68033549
+    ○  kmkuslsw hidden [email protected] 2001-02-03 08:05:18 62f70695
        (empty) (no description set)
     "###);
 }

lib/src/backend.rs

@@ -380,7 +380,7 @@ pub fn make_root_commit(root_change_id: ChangeId, empty_tree_id: TreeId) -> Comm
     Commit {
         parents: vec![],
         predecessors: vec![],
-        root_tree: MergedTreeId::Legacy(empty_tree_id),
+        root_tree: MergedTreeId::resolved(empty_tree_id),
         change_id: root_change_id,
         description: String::new(),
         author: signature.clone(),