sketch: "git add remote sketch-host"

Having a named remote makes working with the sketch container
easier with the terminal and so forth.
diff --git a/loop/agent.go b/loop/agent.go
index dda3aa6..a14d244 100644
--- a/loop/agent.go
+++ b/loop/agent.go
@@ -446,7 +446,12 @@
 		if out, err := cmd.CombinedOutput(); err != nil {
 			return fmt.Errorf("git stash: %s: %v", out, err)
 		}
-		cmd = exec.CommandContext(ctx, "git", "fetch", ini.GitRemoteAddr)
+		cmd = exec.CommandContext(ctx, "git", "remote", "add", "sketch-host", ini.GitRemoteAddr)
+		cmd.Dir = ini.WorkingDir
+		if out, err := cmd.CombinedOutput(); err != nil {
+			return fmt.Errorf("git remote add: %s: %v", out, err)
+		}
+		cmd = exec.CommandContext(ctx, "git", "fetch", "sketch-host")
 		cmd.Dir = ini.WorkingDir
 		if out, err := cmd.CombinedOutput(); err != nil {
 			return fmt.Errorf("git fetch: %s: %w", out, err)