Add Git Worktree Explorer canvas

.github/plugin/marketplace.json

@@ -649,6 +649,12 @@
         "repo": "Azure/git-ape"
       }
     },
+    {
+      "name": "git-worktree-explorer",
+      "source": "extensions/git-worktree-explorer",
+      "description": "Visualize the active Git repository through worktrees, branches, commits, and optional GitHub pull request context.",
+      "version": "1.0.0"
+    },
     {
       "name": "github-copilot-modernization",
       "description": "Autonomous application modernization using multi-agent orchestration for GitHub Copilot CLI. Supports Java upgrades (8→21, Spring Boot 2.x→3.x), .NET modernization, Azure migration, CVE/vulnerability fixing, and application rearchitecture (monolith-to-microservices). Features a 3-level agent hierarchy (orchestrator → coordinators → executors) with enterprise rulebook support for embedding organizational policies into the workflow.",

extensions/git-worktree-explorer/.github/plugin/plugin.json

@@ -0,0 +1,18 @@
+{
+  "name": "git-worktree-explorer",
+  "description": "Visualize the active Git repository through worktrees, branches, commits, and optional GitHub pull request context.",
+  "version": "1.0.0",
+  "author": {
+    "name": "GitHub Copilot"
+  },
+  "keywords": [
+    "branch-visualization",
+    "canvas",
+    "commit-history",
+    "git",
+    "repository-topology",
+    "worktrees"
+  ],
+  "logo": "assets/preview.png",
+  "extensions": "."
+}

extensions/git-worktree-explorer/extension.mjs

@@ -0,0 +1,94 @@
+import { CanvasError, createCanvas, joinSession } from "@github/copilot-sdk/extension";
+import { getServerEntry, refreshServer, startServer, stopServer } from "./server.mjs";
+
+const session = await joinSession({
+    canvases: [
+        createCanvas({
+            id: "git-worktree-explorer",
+            displayName: "Git Worktree Explorer",
+            description: "Explore the active Git repository through worktrees, branches, commits, and related GitHub pull requests.",
+            inputSchema: {
+                type: "object",
+                additionalProperties: false,
+                properties: {
+                    startAt: {
+                        type: "string",
+                        enum: ["repository"],
+                        description: "Initial topology level.",
+                    },
+                },
+            },
+            actions: [
+                {
+                    name: "refresh",
+                    description: "Refresh Git and GitHub information shown by an open explorer.",
+                    inputSchema: {
+                        type: "object",
+                        additionalProperties: false,
+                        properties: {},
+                    },
+                    handler: async (ctx) => {
+                        try {
+                            const snapshot = await refreshServer(ctx.instanceId);
+                            return {
+                                gatheredAt: snapshot.gatheredAt,
+                                worktrees: snapshot.worktrees.length,
+                                branches: snapshot.branches.length,
+                            };
+                        } catch (error) {
+                            throw new CanvasError("git_refresh_failed", error.message);
+                        }
+                    },
+                },
+                {
+                    name: "focus_node",
+                    description: "Ask an open explorer to focus a repository, worktree, or branch node by its canvas node ID.",
+                    inputSchema: {
+                        type: "object",
+                        additionalProperties: false,
+                        properties: {
+                            nodeId: { type: "string", minLength: 1 },
+                        },
+                        required: ["nodeId"],
+                    },
+                    handler: async (ctx) => {
+                        const entry = getServerEntry(ctx.instanceId);
+                        if (!entry) throw new CanvasError("canvas_not_open", "Canvas instance is not open.");
+                        const nodeId = ctx.input?.nodeId;
+                        const snapshot = entry.snapshot;
+                        const exists = nodeId === "repository"
+                            || snapshot.worktrees.some((item) => item.id === nodeId)
+                            || snapshot.branches.some((item) => item.id === nodeId);
+                        if (!exists) throw new CanvasError("git_node_not_found", `Git node not found: ${nodeId}`);
+                        for (const client of entry.clients) {
+                            client.write(`event: focus\ndata: ${JSON.stringify({ nodeId })}\n\n`);
+                        }
+                        return { nodeId };
+                    },
+                },
+            ],
+            open: async (ctx) => {
+                const cwd = ctx.session?.workingDirectory;
+                if (!cwd) {
+                    throw new CanvasError("workspace_unavailable", "The active session working directory is unavailable.");
+                }
+                try {
+                    const entry = await startServer(ctx.instanceId, {
+                        cwd,
+                        sendPrompt: async (prompt) => session.send({ prompt }),
+                    });
+                    return {
+                        title: "Git Worktree Explorer",
+                        status: `${entry.snapshot.worktrees.length} worktrees · ${entry.snapshot.branches.length} branches`,
+                        url: entry.url,
+                    };
+                } catch (error) {
+                    throw new CanvasError("git_repository_unavailable", error.message);
+                }
+            },
+            onClose: async (ctx) => {
+                await stopServer(ctx.instanceId);
+            },
+        }),
+    ],
+});