Add service layer and MCP server with read tools

Slice 1: internal/service is the one capability layer both the HTTP API and the MCP server call (AGENT.md 1.7); /api/repos and /api/repo route through it. Slice 2: internal/mcp serves an MCP server over Streamable HTTP at /mcp (go-sdk v1.8.0) with read tools list_repos and get_repo as thin adapters over the service, plus a round-trip test. Enabled air polling so hot reload works across the Docker-on-Windows bind mount.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
2026-09-19 17:18:40 -04:00
parent dfa45de40c
commit 2d7f814a23
8 changed files with 300 additions and 8 deletions
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// Package mcp exposes GitManager's capabilities to Claude as an MCP server over
// Streamable HTTP (AGENT.md §8.1). The tool handlers are THIN ADAPTERS over the
// shared service layer (§1.7) — no Git/forge logic lives here. Read tools only
// for now; acting/destructive tools arrive with the service methods that back
// them, carrying the §1.4 confirmation contract.
package mcp
import (
"context"
"fmt"
"net/http"
mcpsdk "github.com/modelcontextprotocol/go-sdk/mcp"
"gitmanager/internal/repos"
"gitmanager/internal/service"
)
// getRepoInput is the argument schema for the get_repo tool.
type getRepoInput struct {
Path string `json:"path" jsonschema:"absolute filesystem path of the repository, exactly as returned by list_repos"`
}
// NewServer builds the MCP server and registers the (currently read-only) tools.
func NewServer(svc *service.Service, version string) *mcpsdk.Server {
s := mcpsdk.NewServer(&mcpsdk.Implementation{
Name: "gitmanager",
Title: "GitManager",
Version: version,
Description: "Discover and inspect the user's local Git repositories.",
}, nil)
// list_repos — no arguments (empty struct = object schema with no properties).
mcpsdk.AddTool(s, &mcpsdk.Tool{
Name: "list_repos",
Description: "List every Git repository GitManager has discovered, each with its current branch, dirty/clean state, ahead/behind counts, and remote names.",
}, func(_ context.Context, _ *mcpsdk.CallToolRequest, _ struct{}) (*mcpsdk.CallToolResult, []repos.State, error) {
return nil, svc.ListRepos(), nil
})
// get_repo — details for one already-discovered repository.
mcpsdk.AddTool(s, &mcpsdk.Tool{
Name: "get_repo",
Description: "Get details for one repository: its local branches (with upstreams), recent commits, and remote URLs. The path must be one returned by list_repos.",
}, func(ctx context.Context, _ *mcpsdk.CallToolRequest, in getRepoInput) (*mcpsdk.CallToolResult, repos.Detail, error) {
detail, ok := svc.RepoDetail(ctx, in.Path)
if !ok {
return nil, repos.Detail{}, fmt.Errorf("unknown repository %q — call list_repos for valid paths", in.Path)
}
return nil, detail, nil
})
return s
}
// Handler serves the MCP server over Streamable HTTP. Mount it at /mcp. Like the
// rest of the app it is localhost-bound and unauthenticated (§8.1) — the same
// server instance backs every session.
func Handler(s *mcpsdk.Server) http.Handler {
return mcpsdk.NewStreamableHTTPHandler(func(*http.Request) *mcpsdk.Server {
return s
}, nil)
}
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package mcp
import (
"context"
"encoding/json"
"io"
"log/slog"
"os"
"os/exec"
"path/filepath"
"testing"
"time"
mcpsdk "github.com/modelcontextprotocol/go-sdk/mcp"
"gitmanager/internal/git"
"gitmanager/internal/repos"
"gitmanager/internal/service"
)
// TestMCPRoundTrip exercises the full path: a real temp git repo -> scanner ->
// service -> MCP tools, called by an in-memory MCP client.
func TestMCPRoundTrip(t *testing.T) {
root := t.TempDir()
repoPath := filepath.Join(root, "myrepo")
if err := os.Mkdir(repoPath, 0o755); err != nil {
t.Fatal(err)
}
runGit(t, repoPath, "init", "-b", "main")
runGit(t, repoPath, "config", "user.email", "test@example.com")
runGit(t, repoPath, "config", "user.name", "Test")
if err := os.WriteFile(filepath.Join(repoPath, "README.md"), []byte("hi\n"), 0o644); err != nil {
t.Fatal(err)
}
runGit(t, repoPath, "add", "-A")
runGit(t, repoPath, "commit", "-m", "first commit")
// Populate the index via the real scanner, then build service + MCP server.
log := slog.New(slog.NewTextHandler(io.Discard, nil))
g := git.New("git")
scanner := repos.NewScanner(g, log, []string{root}, 3, nil, time.Minute, false)
scanner.Refresh(context.Background())
svc := service.New(g, scanner.Index)
srv := NewServer(svc, "test")
// Wire an in-memory client<->server session.
ctx := context.Background()
clientT, serverT := mcpsdk.NewInMemoryTransports()
serverSession, err := srv.Connect(ctx, serverT, nil)
if err != nil {
t.Fatalf("server connect: %v", err)
}
defer serverSession.Close()
client := mcpsdk.NewClient(&mcpsdk.Implementation{Name: "test", Version: "0"}, nil)
cs, err := client.Connect(ctx, clientT, nil)
if err != nil {
t.Fatalf("client connect: %v", err)
}
defer cs.Close()
// list_repos should find our one repo.
res, err := cs.CallTool(ctx, &mcpsdk.CallToolParams{Name: "list_repos"})
if err != nil {
t.Fatalf("list_repos: %v", err)
}
var states []repos.State
decodeResult(t, res, &states)
if len(states) != 1 {
t.Fatalf("expected 1 repo, got %d: %+v", len(states), states)
}
if states[0].Name != "myrepo" || states[0].Branch != "main" {
t.Fatalf("unexpected repo state: %+v", states[0])
}
// get_repo should return detail including the commit we made.
res, err = cs.CallTool(ctx, &mcpsdk.CallToolParams{
Name: "get_repo",
Arguments: map[string]any{"path": states[0].Path},
})
if err != nil {
t.Fatalf("get_repo: %v", err)
}
var detail repos.Detail
decodeResult(t, res, &detail)
if len(detail.Commits) != 1 || detail.Commits[0].Subject != "first commit" {
t.Fatalf("unexpected detail commits: %+v", detail.Commits)
}
// get_repo with a bad path is a tool error, not a protocol error.
res, err = cs.CallTool(ctx, &mcpsdk.CallToolParams{
Name: "get_repo",
Arguments: map[string]any{"path": filepath.Join(root, "nope")},
})
if err != nil {
t.Fatalf("get_repo(bad) protocol error: %v", err)
}
if !res.IsError {
t.Fatalf("expected IsError for unknown repo, got success")
}
}
// decodeResult unmarshals the JSON text content of a tool result into v.
func decodeResult(t *testing.T, res *mcpsdk.CallToolResult, v any) {
t.Helper()
for _, c := range res.Content {
if tc, ok := c.(*mcpsdk.TextContent); ok {
if err := json.Unmarshal([]byte(tc.Text), v); err != nil {
t.Fatalf("unmarshal result: %v (text=%s)", err, tc.Text)
}
return
}
}
t.Fatalf("no text content in result: %+v", res.Content)
}
func runGit(t *testing.T, dir string, args ...string) {
t.Helper()
cmd := exec.Command("git", args...)
cmd.Dir = dir
if out, err := cmd.CombinedOutput(); err != nil {
t.Fatalf("git %v: %v\n%s", args, err, out)
}
}