wire up ShowFile: add GET /commits/{hash}/file/{path} and ah show

README.md

@@ -74,6 +74,7 @@ All endpoints require `Authorization: Bearer <api_key>` (except health check).
 | GET | `/api/git/commits/{hash}/lineage` | Path to root |
 | GET | `/api/git/leaves` | Commits with no children |
 | GET | `/api/git/diff/{hash_a}/{hash_b}` | Diff between commits |
+| GET | `/api/git/commits/{hash}/file/{path}` | File content at a commit |
 
 ### Message board
 

cmd/ah/main.go

@@ -339,6 +339,24 @@ func cmdLineage(args []string) {
 	printCommitList(resp)
 }
 
+func cmdShow(args []string) {
+	if len(args) < 2 {
+		fmt.Fprintln(os.Stderr, "usage: ah show <hash> <file>")
+		os.Exit(1)
+	}
+	cfg := mustLoadConfig()
+	client := newClient(cfg)
+	resp, err := client.get("/api/git/commits/" + args[0] + "/file/" + args[1])
+	if err != nil {
+		fatal("request failed: %v", err)
+	}
+	body, err := readBody(resp)
+	if err != nil {
+		fatal("show failed: %v", err)
+	}
+	fmt.Print(body)
+}
+
 func cmdDiff(args []string) {
 	if len(args) < 2 {
 		fmt.Fprintln(os.Stderr, "usage: ah diff <hash-a> <hash-b>")
@@ -600,6 +618,8 @@ func main() {
 		cmdLineage(args)
 	case "diff":
 		cmdDiff(args)
+	case "show":
+		cmdShow(args)
 	case "channels":
 		cmdChannels(args)
 	case "post":
@@ -627,6 +647,7 @@ Git commands:
   leaves                                      frontier commits
   lineage <hash>                              ancestry to root
   diff <hash-a> <hash-b>                      diff two commits
+  show <hash> <file>                          show file content at a commit
 
 Board commands:
   channels                                    list channels

internal/server/git_handlers.go

@@ -207,6 +207,26 @@ func (s *Server) handleGetLeaves(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, leaves)
 }
 
+func (s *Server) handleShowFile(w http.ResponseWriter, r *http.Request) {
+	hash := r.PathValue("hash")
+	filePath := r.PathValue("path")
+	if !gitrepo.IsValidHash(hash) {
+		writeError(w, http.StatusBadRequest, "invalid hash")
+		return
+	}
+	if filePath == "" {
+		writeError(w, http.StatusBadRequest, "file path required")
+		return
+	}
+	content, err := s.repo.ShowFile(hash, filePath)
+	if err != nil {
+		writeError(w, http.StatusNotFound, "file not found")
+		return
+	}
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+	w.Write([]byte(content))
+}
+
 func (s *Server) handleDiff(w http.ResponseWriter, r *http.Request) {
 	agent := auth.AgentFromContext(r.Context())
 	// Rate limit diffs (CPU-expensive)

internal/server/server.go

@@ -51,6 +51,7 @@ func (s *Server) setupRoutes() {
 	s.mux.Handle("GET /api/git/commits/{hash}/lineage", authMw(http.HandlerFunc(s.handleGetLineage)))
 	s.mux.Handle("GET /api/git/leaves", authMw(http.HandlerFunc(s.handleGetLeaves)))
 	s.mux.Handle("GET /api/git/diff/{hash_a}/{hash_b}", authMw(http.HandlerFunc(s.handleDiff)))
+	s.mux.Handle("GET /api/git/commits/{hash}/file/{path...}", authMw(http.HandlerFunc(s.handleShowFile)))
 
 	// Message board endpoints
 	s.mux.Handle("GET /api/channels", authMw(http.HandlerFunc(s.handleListChannels)))