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:
  * if any decendants are conflict free: "Conflict fixed in <decendant>". For
    this, print the short_change_hash of the first decendant without conflicts.
  * if no decendants are conflict free: Print the existing message we print today.

* If working commit has no conflicts:
  * If any parent has conflicts: "Conflict in parent is resolved in working copy".
    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.

* Rename existing unittest
* Also update Changelog here

CHANGELOG.md

@@ -101,6 +101,10 @@ 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 has
+  fixed the conflict, 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

@@ -17,7 +17,7 @@ use jj_lib::repo::Repo;
 use jj_lib::revset::{RevsetExpression, RevsetFilterPredicate};
 use tracing::instrument;
 
-use crate::cli_util::{print_conflicted_paths, CommandHelper};
+use crate::cli_util::{print_conflicted_paths, short_change_hash, CommandHelper};
 use crate::command_error::CommandError;
 use crate::diff_util::DiffFormat;
 use crate::revset_util;
@@ -91,21 +91,54 @@ 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());
+
+            if let Some(first_descendant_no_conflict) = workspace_command
+                .attach_revset_evaluator(
+                    wc_revset
+                        .children()
+                        .descendants()
+                        .filtered(RevsetFilterPredicate::HasNoConflict),
+                )?
+                .evaluate_to_commits()?
+                .collect::<Vec<_>>()
+                .pop()
+            {
+                writeln!(
+                    formatter.labeled("conflict"),
+                    "Conflict has been resolved in descendants: {}",
+                    short_change_hash(first_descendant_no_conflict?.change_id())
+                )?;
+            } else {
+                // Ancestors with conflicts, excluding the current working copy commit.
+                let ancestors_conflicts: Vec<_> = 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("conflict"),
+                        "Conflict in parent commit has been resolved in working copy"
+                    )?;
+                    break;
+                }
+            }
+        }
     } else {
         writeln!(formatter, "No working copy")?;
     }

cli/tests/test_status_command.rs

@@ -106,7 +106,7 @@ fn test_status_filtered() {
 
 // See <https://github.com/martinvonz/jj/issues/3108>
 #[test]
-fn test_status_display_rebase_instructions() {
+fn test_status_display_rebase_instructions_if_no_descendant_resolves_conflict() {
     let test_env = TestEnvironment::default();
     test_env.jj_cmd_ok(test_env.env_root(), &["git", "init", "repo"]);
 
@@ -177,6 +177,81 @@ fn test_status_display_rebase_instructions() {
     "###);
 }
 
+#[test]
+fn test_status_display_if_child_resolves_conflict() {
+    let test_env = TestEnvironment::default();
+    test_env.jj_cmd_ok(test_env.env_root(), &["git", "init", "repo"]);
+
+    let repo_path = test_env.env_root().join("repo");
+    let conflicted_path = repo_path.join("conflicted.txt");
+
+    // PARENT: Write the initial file
+    std::fs::write(&conflicted_path, "initial contents").unwrap();
+    test_env.jj_cmd_ok(&repo_path, &["describe", "--message", "Initial contents"]);
+
+    // CHILD1: New commit on top of <PARENT>
+    test_env.jj_cmd_ok(
+        &repo_path,
+        &["new", "--message", "First part of conflicting change"],
+    );
+    std::fs::write(&conflicted_path, "Child 1").unwrap();
+
+    // CHILD2: New commit also on top of <PARENT>
+    test_env.jj_cmd_ok(
+        &repo_path,
+        &[
+            "new",
+            "--message",
+            "Second part of conflicting change",
+            "@-",
+        ],
+    );
+    std::fs::write(&conflicted_path, "Child 2").unwrap();
+
+    // CONFLICT: New commit that is conflicted by merging <CHILD1> and <CHILD2>
+    test_env.jj_cmd_ok(&repo_path, &["new", "--message", "boom", "all:(@-)+"]);
+    // Adding more descendants to ensure we correctly find the root ancestors with
+    // conflicts, not just the parents.
+    test_env.jj_cmd_ok(&repo_path, &["new", "--message", "boom-cont"]);
+    test_env.jj_cmd_ok(&repo_path, &["new", "--message", "fix_conflict1"]);
+    std::fs::write(&conflicted_path, "first commit to fix conflict").unwrap();
+    test_env.jj_cmd_ok(
+        &repo_path,
+        &["new", "--message", "child of conflict fixing commit"],
+    );
+
+    let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-r", "::@"]);
+
+    insta::assert_snapshot!(stdout, @r###"
+    @  vruxwmqv [email protected] 2001-02-03 08:05:14 c6ea5f6c
+    │  (empty) child of conflict fixing commit
+    ○  yqosqzyt [email protected] 2001-02-03 08:05:14 15837663
+    │  fix_conflict1
+    ×  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###"
+    The working copy is clean
+    There are unresolved conflicts at these paths:
+    conflicted.txt    2-sided conflict
+    Working copy : yqosqzyt 65143fef (conflict) (empty) boom-cont-2
+    Parent commit: royxmykx a4e88714 (conflict) (empty) boom-cont
+    Conflict has been resolved in descendant: foobar
+    "###);
+}
+
 #[test]
 fn test_status_simplify_conflict_sides() {
     let test_env = TestEnvironment::default();