log: optionally render elided parts of the graph as a synthetic node

This adds a config to render a synthetic node with a "(elided
revisions)" description for elided segments of the graph.

I didn't add any templating support for the elided nodes because I'm
not sure how we would want that to work. In particular, I don't know
what `commit_id` and most other keywords should return for elided
revisions.

CHANGELOG.md

@@ -40,6 +40,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * Built-in pager based on [minus](https://github.com/arijit79/minus/)
 
+* Set config `ui.log-synthetic-elided-nodes = true` to make `jj log` include
+  synthetic nodes in the graph where some revisions were elided
+  ([#1252](https://github.com/martinvonz/jj/issues/1252),
+  [#2971](https://github.com/martinvonz/jj/issues/2971)). This may become the
+  default depending on feedback.
+
 ### Fixed bugs
 
 * On Windows, symlinks in the repo are now materialized as regular files in the

cli/src/commands/log.rs

@@ -104,6 +104,10 @@ pub(crate) fn cmd_log(
         Some(value) => value.to_string(),
         None => command.settings().config().get_string("templates.log")?,
     };
+    let use_elided_nodes = command
+        .settings()
+        .config()
+        .get_bool("ui.log-synthetic-elided-nodes")?;
     let template = workspace_command.parse_commit_template(&template_string)?;
     let with_content_format = LogContentFormat::new(ui, command.settings())?;
 
@@ -115,42 +119,58 @@ pub(crate) fn cmd_log(
         if !args.no_graph {
             let mut graph = get_graphlog(command.settings(), formatter.raw());
             let default_node_symbol = graph.default_node_symbol().to_owned();
+            let elided_node_symbol = graph.elided_node_symbol().to_owned();
             let forward_iter = TopoGroupedRevsetGraphIterator::new(revset.iter_graph());
             let iter: Box<dyn Iterator<Item = _>> = if args.reversed {
                 Box::new(ReverseRevsetGraphIterator::new(forward_iter))
             } else {
                 Box::new(forward_iter)
             };
             for (commit_id, edges) in iter.take(args.limit.unwrap_or(usize::MAX)) {
+                // The graph is keyed by (CommitId, is_synthetic)
                 let mut graphlog_edges = vec![];
                 // TODO: Should we update RevsetGraphIterator to yield this flag instead of all
                 // the missing edges since we don't care about where they point here
                 // anyway?
                 let mut has_missing = false;
+                let mut elided_targets = vec![];
                 for edge in edges {
                     match edge.edge_type {
                         RevsetGraphEdgeType::Missing => {
                             has_missing = true;
                         }
-                        RevsetGraphEdgeType::Direct => graphlog_edges.push(Edge::Present {
-                            direct: true,
-                            target: edge.target,
-                        }),
-                        RevsetGraphEdgeType::Indirect => graphlog_edges.push(Edge::Present {
-                            direct: false,
-                            target: edge.target,
-                        }),
+                        RevsetGraphEdgeType::Direct => {
+                            graphlog_edges.push(Edge::Present {
+                                direct: true,
+                                target: (edge.target, false),
+                            });
+                        }
+                        RevsetGraphEdgeType::Indirect => {
+                            if use_elided_nodes {
+                                elided_targets.push(edge.target.clone());
+                                graphlog_edges.push(Edge::Present {
+                                    direct: true,
+                                    target: (edge.target, true),
+                                });
+                            } else {
+                                graphlog_edges.push(Edge::Present {
+                                    direct: false,
+                                    target: (edge.target, false),
+                                });
+                            }
+                        }
                     }
                 }
                 if has_missing {
                     graphlog_edges.push(Edge::Missing);
                 }
                 let mut buffer = vec![];
-                let commit = store.get_commit(&commit_id)?;
+                let key = (commit_id, false);
+                let commit = store.get_commit(&key.0)?;
                 with_content_format.write_graph_text(
                     ui.new_formatter(&mut buffer).as_mut(),
                     |formatter| template.format(&commit, formatter),
-                    || graph.width(&commit_id, &graphlog_edges),
+                    || graph.width(&key, &graphlog_edges),
                 )?;
                 if !buffer.ends_with(b"\n") {
                     buffer.push(b'\n');
@@ -166,18 +186,38 @@ pub(crate) fn cmd_log(
                         &diff_formats,
                     )?;
                 }
-                let node_symbol = if Some(&commit_id) == wc_commit_id {
+                let node_symbol = if Some(&key.0) == wc_commit_id {
                     "@"
                 } else {
                     &default_node_symbol
                 };
 
                 graph.add_node(
-                    &commit_id,
+                    &key,
                     &graphlog_edges,
                     node_symbol,
                     &String::from_utf8_lossy(&buffer),
                 )?;
+                for elided_target in elided_targets {
+                    let elided_key = (elided_target, true);
+                    let real_key = (elided_key.0.clone(), false);
+                    let edges = [Edge::Present {
+                        direct: true,
+                        target: real_key,
+                    }];
+                    let mut buffer = vec![];
+                    with_content_format.write_graph_text(
+                        ui.new_formatter(&mut buffer).as_mut(),
+                        |formatter| writeln!(formatter.labeled("elided"), "(elided revisions)"),
+                        || graph.width(&elided_key, &edges),
+                    )?;
+                    graph.add_node(
+                        &elided_key,
+                        &edges,
+                        &elided_node_symbol,
+                        &String::from_utf8_lossy(&buffer),
+                    )?;
+                }
             }
         } else {
             let iter: Box<dyn Iterator<Item = CommitId>> = if args.reversed {

cli/src/config-schema.json

@@ -119,6 +119,11 @@
                     "description": "Whether to wrap log template output",
                     "default": false
                 },
+                "log-synthetic-elided-nodes": {
+                    "type": "boolean",
+                    "description": "Whether to render elided parts of the graph as synthetic nodes.",
+                    "default": false
+                },
                 "editor": {
                     "type": "string",
                     "description": "Editor to use for commands that involve editing text"
@@ -381,4 +386,4 @@
             }
         }
     }
-}
+}

cli/src/config/colors.toml

@@ -10,10 +10,10 @@
 "change_id" = "magenta"
 
 # Unique prefixes and the rest for change & commit ids
-"prefix" = { bold = true}
+"prefix" = { bold = true }
 "rest" = "bright black"
 "divergent rest" = "red"
-"divergent prefix" = {fg = "red", underline=true}
+"divergent prefix" = { fg = "red", underline = true }
 "hidden prefix" = "default"
 
 "email" = "yellow"
@@ -28,13 +28,14 @@
 "git_refs" = "green"
 "git_head" = "green"
 "divergent" = "red"
-"divergent change_id"="red"
+"divergent change_id" = "red"
 "conflict" = "red"
 "empty" = "green"
 "placeholder" = "red"
 "description placeholder" = "yellow"
 "empty description placeholder" = "green"
 "separator" = "bright black"
+"elided" = "bright black"
 "root" = "green"
 
 "working_copy" = { bold = true }
@@ -45,13 +46,13 @@
 "working_copy email" = "yellow"
 "working_copy timestamp" = "bright cyan"
 "working_copy working_copies" = "bright magenta"
-"working_copy branch"  = "bright magenta"
+"working_copy branch" = "bright magenta"
 "working_copy branches" = "bright magenta"
 "working_copy local_branches" = "bright magenta"
 "working_copy remote_branches" = "bright magenta"
 "working_copy tags" = "bright magenta"
 "working_copy git_refs" = "bright green"
-"working_copy divergent" =  "bright red"
+"working_copy divergent" = "bright red"
 "working_copy divergent change_id" = "bright red"
 "working_copy conflict" = "bright red"
 "working_copy empty" = "bright green"
@@ -71,5 +72,5 @@
 "op_log time" = "cyan"
 "op_log current_operation" = { bold = true }
 "op_log current_operation id" = "bright blue"
-"op_log current_operation user" = "yellow"  # No bright yellow, see comment above
+"op_log current_operation user" = "yellow"                    # No bright yellow, see comment above
 "op_log current_operation time" = "bright cyan"

cli/src/config/misc.toml

@@ -8,6 +8,7 @@ tree-level-conflicts = true
 paginate = "auto"
 pager = { command = ["less", "-FRX"], env = { LESSCHARSET = "utf-8" } }
 log-word-wrap = false
+log-synthetic-elided-nodes = false
 
 [snapshot]
 max-new-file-size = "1MiB"

cli/src/graphlog.rs

@@ -58,13 +58,16 @@ pub trait GraphLog<K: Clone + Eq + Hash> {
 
     fn default_node_symbol(&self) -> &str;
 
+    fn elided_node_symbol(&self) -> &str;
+
     fn width(&self, id: &K, edges: &[Edge<K>]) -> usize;
 }
 
 pub struct SaplingGraphLog<'writer, R> {
     renderer: R,
     writer: &'writer mut dyn Write,
     default_node_symbol: String,
+    elided_node_symbol: String,
 }
 
 impl<K: Clone> From<&Edge<K>> for Ancestor<K> {
@@ -106,6 +109,10 @@ where
         &self.default_node_symbol
     }
 
+    fn elided_node_symbol(&self) -> &str {
+        &self.elided_node_symbol
+    }
+
     fn width(&self, id: &K, edges: &[Edge<K>]) -> usize {
         let parents = edges.iter().map_into().collect();
         let w: u64 = self.renderer.width(Some(id), Some(&parents));
@@ -118,6 +125,7 @@ impl<'writer, R> SaplingGraphLog<'writer, R> {
         renderer: R,
         formatter: &'writer mut dyn Write,
         default_node_symbol: &str,
+        elided_node_symbol: &str,
     ) -> Box<dyn GraphLog<K> + 'writer>
     where
         K: Clone + Eq + Hash + 'writer,
@@ -127,6 +135,7 @@ impl<'writer, R> SaplingGraphLog<'writer, R> {
             renderer,
             writer: formatter,
             default_node_symbol: default_node_symbol.to_owned(),
+            elided_node_symbol: elided_node_symbol.to_owned(),
         })
     }
 }
@@ -142,10 +151,11 @@ pub fn get_graphlog<'a, K: Clone + Eq + Hash + 'a>(
             builder.build_box_drawing().with_square_glyphs(),
             formatter,
             "◉",
+            "◌",
         ),
-        "ascii" => SaplingGraphLog::create(builder.build_ascii(), formatter, "o"),
-        "ascii-large" => SaplingGraphLog::create(builder.build_ascii_large(), formatter, "o"),
+        "ascii" => SaplingGraphLog::create(builder.build_ascii(), formatter, "o", "."),
+        "ascii-large" => SaplingGraphLog::create(builder.build_ascii_large(), formatter, "o", "."),
         // "curved"
-        _ => SaplingGraphLog::create(builder.build_box_drawing(), formatter, "◉"),
+        _ => SaplingGraphLog::create(builder.build_box_drawing(), formatter, "◉", "◌"),
     }
 }

cli/tests/test_log_command.rs

@@ -1333,3 +1333,101 @@ fn test_log_word_wrap() {
        merge
     "###);
 }
+
+#[test]
+fn test_elided() {
+    // Test that elided commits are shown as synthetic nodes.
+    let test_env = TestEnvironment::default();
+    test_env.jj_cmd_ok(test_env.env_root(), &["init", "repo", "--git"]);
+    let repo_path = test_env.env_root().join("repo");
+
+    test_env.jj_cmd_ok(&repo_path, &["describe", "-m", "initial"]);
+    test_env.jj_cmd_ok(&repo_path, &["new", "-m", "main branch 1"]);
+    test_env.jj_cmd_ok(&repo_path, &["new", "-m", "main branch 2"]);
+    test_env.jj_cmd_ok(&repo_path, &["new", "@--", "-m", "side branch 1"]);
+    test_env.jj_cmd_ok(&repo_path, &["new", "-m", "side branch 2"]);
+    test_env.jj_cmd_ok(
+        &repo_path,
+        &["new", "-m", "merge", r#"description("main branch 2")"#, "@"],
+    );
+
+    let get_log = |revs: &str| -> String {
+        test_env.jj_cmd_success(
+            &repo_path,
+            &["log", "-T", r#"description ++ "\n""#, "-r", revs],
+        )
+    };
+
+    // Test the setup
+    insta::assert_snapshot!(get_log("::"), @r###"
+    @    merge
+    ├─╮
+    │ ◉  side branch 2
+    │ │
+    │ ◉  side branch 1
+    │ │
+    ◉ │  main branch 2
+    │ │
+    ◉ │  main branch 1
+    ├─╯
+    ◉  initial
+    │
+    ◉
+    "###);
+
+    // Elide some commits from each side of the merge. It's unclear that a revision
+    // was skipped on the left side.
+    insta::assert_snapshot!(get_log("@ | @- | description(initial)"), @r###"
+    @    merge
+    ├─╮
+    │ ◉  side branch 2
+    │ ╷
+    ◉ ╷  main branch 2
+    ├─╯
+    ◉  initial
+    │
+    ~
+    "###);
+
+    // Elide shared commits. It's unclear that a revision was skipped on the right
+    // side (#1252).
+    insta::assert_snapshot!(get_log("@-- | root()"), @r###"
+    ◉  side branch 1
+    ╷
+    ╷ ◉  main branch 1
+    ╭─╯
+    ◉
+    "###);
+
+    // Now test the same thing with synthetic nodes for elided commits
+
+    // Elide some commits from each side of the merge
+    test_env.add_config("ui.log-synthetic-elided-nodes = true");
+    insta::assert_snapshot!(get_log("@ | @- | description(initial)"), @r###"
+    @    merge
+    ├─╮
+    │ ◉  side branch 2
+    │ │
+    │ ◌  (elided revisions)
+    ◉ │  main branch 2
+    │ │
+    ◌ │  (elided revisions)
+    ├─╯
+    ◉  initial
+    │
+    ~
+    "###);
+
+    // Elide shared commits. To keep the implementation simple, it still gets
+    // rendered as two synthetic nodes.
+    insta::assert_snapshot!(get_log("@-- | root()"), @r###"
+    ◉  side branch 1
+    │
+    ◌  (elided revisions)
+    │ ◉  main branch 1
+    │ │
+    │ ◌  (elided revisions)
+    ├─╯
+    ◉
+    "###);
+}