fix: validate repo URL format on app creation (closes #88)

internal/handlers/repo_url_validation.go

@@ -0,0 +1,61 @@
+package handlers
+
+import (
+	"errors"
+	"net/url"
+	"regexp"
+	"strings"
+)
+
+// Repo URL validation errors.
+var (
+	errRepoURLEmpty   = errors.New("repository URL must not be empty")
+	errRepoURLScheme  = errors.New("file:// URLs are not allowed for security reasons")
+	errRepoURLInvalid = errors.New("repository URL must use https://, http://, ssh://, git://, or git@host:path format")
+	errRepoURLNoHost  = errors.New("repository URL must include a host")
+	errRepoURLNoPath  = errors.New("repository URL must include a path")
+)
+
+// scpLikeRepoRe matches SCP-like git URLs: git@host:path (e.g. git@github.com:user/repo.git).
+var scpLikeRepoRe = regexp.MustCompile(`^[a-zA-Z0-9._-]+@[a-zA-Z0-9._-]+:.+$`)
+
+// validateRepoURL checks that the given repository URL is valid and uses an allowed scheme.
+func validateRepoURL(repoURL string) error {
+	if strings.TrimSpace(repoURL) == "" {
+		return errRepoURLEmpty
+	}
+
+	// Check for SCP-like git URLs first (git@host:path)
+	if scpLikeRepoRe.MatchString(repoURL) {
+		return nil
+	}
+
+	// Reject file:// explicitly
+	if strings.HasPrefix(strings.ToLower(repoURL), "file://") {
+		return errRepoURLScheme
+	}
+
+	// Parse as standard URL
+	parsed, err := url.Parse(repoURL)
+	if err != nil {
+		return errRepoURLInvalid
+	}
+
+	// Must have a recognized scheme
+	switch strings.ToLower(parsed.Scheme) {
+	case "https", "http", "ssh", "git":
+		// OK
+	default:
+		return errRepoURLInvalid
+	}
+
+	if parsed.Host == "" {
+		return errRepoURLNoHost
+	}
+
+	if parsed.Path == "" || parsed.Path == "/" {
+		return errRepoURLNoPath
+	}
+
+	return nil
+}