Change conflict hint depending on state of working commit.

To avoid always printing the rebase instructions to fix a conflict
even when a child commit to fix the conflict already exists, implement
the following:

* If working commit has conflicts:
  * Continue printing the same message we print today.

* If working commit has no conflicts:
  * If any parent has conflicts, we print: "Conflict in parent is resolved in working copy".
    Also explicitly not printing the "conflicting parent" here, since a merge commit
    could have conflict in multiple parents.
  * If no parent has any conflicts: exit quietly.
* Update unittests for conflict hinting update.
* Update CHANGELOG

CHANGELOG.md

@@ -101,6 +101,11 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ### Fixed bugs
 
+* `jj status` will show different messages in a conflicted tree, depending
+  on the state of the working commit. In particular, if a child commit fixes
+  a conflict in the parent, this will be reflected in the hint provided
+  by `jj status`
+
 * `jj diff --git` no longer shows the contents of binary files.
 
 * Windows binaries no longer require `vcruntime140.dll` to be installed

cli/src/commands/status.rs

@@ -92,21 +92,36 @@ pub(crate) fn cmd_status(
             writeln!(formatter)?;
         }
 
-        let wc_revset = RevsetExpression::commit(wc_commit.id().clone());
-        // Ancestors with conflicts, excluding the current working copy commit.
-        let ancestors_conflicts = workspace_command
-            .attach_revset_evaluator(
-                wc_revset
-                    .parents()
-                    .ancestors()
-                    .filtered(RevsetFilterPredicate::HasConflict)
-                    .minus(&revset_util::parse_immutable_expression(
-                        &workspace_command.revset_parse_context(),
-                    )?),
-            )?
-            .evaluate_to_commit_ids()?
-            .collect();
-        workspace_command.report_repo_conflicts(formatter, repo, ancestors_conflicts)?;
+        if wc_commit.has_conflict()? {
+            let wc_revset = RevsetExpression::commit(wc_commit.id().clone());
+
+            // Ancestors with conflicts, excluding the current working copy commit.
+            let ancestors_conflicts = workspace_command
+                .attach_revset_evaluator(
+                    wc_revset
+                        .parents()
+                        .ancestors()
+                        .filtered(RevsetFilterPredicate::HasConflict)
+                        .minus(&revset_util::parse_immutable_expression(
+                            &workspace_command.revset_parse_context(),
+                        )?),
+                )?
+                .evaluate_to_commit_ids()?
+                .collect();
+
+            workspace_command.report_repo_conflicts(formatter, repo, ancestors_conflicts)?;
+        } else {
+            for parent in wc_commit.parents() {
+                let parent = parent?;
+                if parent.has_conflict()? {
+                    writeln!(
+                        formatter.labeled("hint"),
+                        "Conflict in parent commit has been resolved in working copy"
+                    )?;
+                    break;
+                }
+            }
+        }
     } else {
         writeln!(formatter, "No working copy")?;
     }

cli/tests/test_status_command.rs

@@ -105,8 +105,9 @@ fn test_status_filtered() {
 }
 
 // See <https://github.com/martinvonz/jj/issues/3108>
+// See <https://github.com/martinvonz/jj/issues/4147>
 #[test]
-fn test_status_display_rebase_instructions() {
+fn test_status_display_relevant_working_commit_conflict_hints() {
     let test_env = TestEnvironment::default();
     test_env.jj_cmd_ok(test_env.env_root(), &["git", "init", "repo"]);
 
@@ -143,7 +144,7 @@ fn test_status_display_rebase_instructions() {
     test_env.jj_cmd_ok(&repo_path, &["new", "--message", "boom-cont"]);
     test_env.jj_cmd_ok(&repo_path, &["new", "--message", "boom-cont-2"]);
 
-    let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-r", "::@"]);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-r", "::"]);
 
     insta::assert_snapshot!(stdout, @r###"
     @  yqosqzyt [email protected] 2001-02-03 08:05:13 65143fef conflict
@@ -175,6 +176,116 @@ fn test_status_display_rebase_instructions() {
     Once the conflicts are resolved, you may want to inspect the result with `jj diff`.
     Then run `jj squash` to move the resolution into the conflicted commit.
     "###);
+
+    // Resolve conflict
+    test_env.jj_cmd_ok(&repo_path, &["new", "--message", "fixed 1"]);
+    std::fs::write(&conflicted_path, "first commit to fix conflict").unwrap();
+
+    // Add one more commit atop the commit that resolves the conflict.
+    test_env.jj_cmd_ok(&repo_path, &["new", "--message", "fixed 2"]);
+    std::fs::write(&conflicted_path, "edit not conflict").unwrap();
+
+    // wc is now conflict free, parent is also conflict free
+    let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-r", "::"]);
+
+    insta::assert_snapshot!(stdout, @r###"
+    @  kpqxywon [email protected] 2001-02-03 08:05:18 3432159f
+    │  fixed 2
+    ○  znkkpsqq [email protected] 2001-02-03 08:05:17 897d589f
+    │  fixed 1
+    ×  yqosqzyt [email protected] 2001-02-03 08:05:13 65143fef conflict
+    │  (empty) boom-cont-2
+    ×  royxmykx [email protected] 2001-02-03 08:05:12 a4e88714 conflict
+    │  (empty) boom-cont
+    ×    mzvwutvl [email protected] 2001-02-03 08:05:11 538415e7 conflict
+    ├─╮  (empty) boom
+    │ ○  kkmpptxz [email protected] 2001-02-03 08:05:10 1e8c2956
+    │ │  First part of conflicting change
+    ○ │  zsuskuln [email protected] 2001-02-03 08:05:11 2c8b19fd
+    ├─╯  Second part of conflicting change
+    ○  qpvuntsm [email protected] 2001-02-03 08:05:08 aade7195
+    │  Initial contents
+    ◆  zzzzzzzz root() 00000000
+    "###);
+
+    let stdout = test_env.jj_cmd_success(&repo_path, &["status"]);
+
+    insta::assert_snapshot!(stdout, @r###"
+    Working copy changes:
+    M conflicted.txt
+    Working copy : kpqxywon 3432159f fixed 2
+    Parent commit: znkkpsqq 897d589f fixed 1
+    "###);
+
+    // Step back one.
+    // wc is still conflict free, parent has a conflict.
+    test_env.jj_cmd_ok(&repo_path, &["edit", "@-"]);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-r", "::"]);
+
+    insta::assert_snapshot!(stdout, @r###"
+    ○  kpqxywon [email protected] 2001-02-03 08:05:18 3432159f
+    │  fixed 2
+    @  znkkpsqq [email protected] 2001-02-03 08:05:17 897d589f
+    │  fixed 1
+    ×  yqosqzyt [email protected] 2001-02-03 08:05:13 65143fef conflict
+    │  (empty) boom-cont-2
+    ×  royxmykx [email protected] 2001-02-03 08:05:12 a4e88714 conflict
+    │  (empty) boom-cont
+    ×    mzvwutvl [email protected] 2001-02-03 08:05:11 538415e7 conflict
+    ├─╮  (empty) boom
+    │ ○  kkmpptxz [email protected] 2001-02-03 08:05:10 1e8c2956
+    │ │  First part of conflicting change
+    ○ │  zsuskuln [email protected] 2001-02-03 08:05:11 2c8b19fd
+    ├─╯  Second part of conflicting change
+    ○  qpvuntsm [email protected] 2001-02-03 08:05:08 aade7195
+    │  Initial contents
+    ◆  zzzzzzzz root() 00000000
+    "###);
+
+    let stdout = test_env.jj_cmd_success(&repo_path, &["status"]);
+
+    insta::assert_snapshot!(stdout, @r###"
+    Working copy changes:
+    M conflicted.txt
+    Working copy : znkkpsqq 897d589f fixed 1
+    Parent commit: yqosqzyt 65143fef (conflict) (empty) boom-cont-2
+    Conflict in parent commit has been resolved in working copy
+    "###);
+
+    // Step back to all the way to `root()+` so that wc has no conflict, even though
+    // there is a conflict later in the tree. So that we can confirm
+    // our hinting logic doesn't get confused.
+    test_env.jj_cmd_ok(&repo_path, &["edit", "root()+"]);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-r", "::"]);
+
+    insta::assert_snapshot!(stdout, @r###"
+    ○  kpqxywon [email protected] 2001-02-03 08:05:18 3432159f
+    │  fixed 2
+    ○  znkkpsqq [email protected] 2001-02-03 08:05:17 897d589f
+    │  fixed 1
+    ×  yqosqzyt [email protected] 2001-02-03 08:05:13 65143fef conflict
+    │  (empty) boom-cont-2
+    ×  royxmykx [email protected] 2001-02-03 08:05:12 a4e88714 conflict
+    │  (empty) boom-cont
+    ×    mzvwutvl [email protected] 2001-02-03 08:05:11 538415e7 conflict
+    ├─╮  (empty) boom
+    │ ○  kkmpptxz [email protected] 2001-02-03 08:05:10 1e8c2956
+    │ │  First part of conflicting change
+    ○ │  zsuskuln [email protected] 2001-02-03 08:05:11 2c8b19fd
+    ├─╯  Second part of conflicting change
+    @  qpvuntsm [email protected] 2001-02-03 08:05:08 aade7195
+    │  Initial contents
+    ◆  zzzzzzzz root() 00000000
+    "###);
+
+    let stdout = test_env.jj_cmd_success(&repo_path, &["status"]);
+
+    insta::assert_snapshot!(stdout, @r###"
+    Working copy changes:
+    A conflicted.txt
+    Working copy : qpvuntsm aade7195 Initial contents
+    Parent commit: zzzzzzzz 00000000 (empty) (no description set)
+    "###);
 }
 
 #[test]