webdav: escape reserved characters in URL path segments

Use URLPathEscapeAll instead of URLPathEscape for path encoding.

URLPathEscape relies on Go's url.URL.String() which only minimally
escapes paths - reserved sub-delimiter characters like semicolons and
equals signs pass through unescaped. Per RFC 3986 section 3.3, these
characters must be percent-encoded when used as literal values in
path segments.

Some WebDAV servers (notably dCache/Jetty) interpret unescaped
semicolons as path parameter delimiters, which truncates filenames
at the semicolon position. URLPathEscapeAll encodes everything
except [A-Za-z0-9/], which is safe for all servers.

Fixes #9082

backend/webdav/webdav.go

@@ -423,7 +423,7 @@ func (f *Fs) filePath(file string) string {
 	if f.opt.Enc != encoder.EncodeZero {
 		subPath = f.opt.Enc.FromStandardPath(subPath)
 	}
-	return rest.URLPathEscape(subPath)
+	return rest.URLPathEscapeAll(subPath)
 }
 
 // dirPath returns a directory path (f.root, dir)

backend/webdav/webdav_internal_test.go

@@ -80,3 +80,35 @@ func TestHeaders(t *testing.T) {
 	_, err := f.Features().About(context.Background())
 	require.NoError(t, err)
 }
+
+// TestReservedCharactersInPathAreEscaped verifies that reserved characters
+// like semicolons and equals signs in file paths are percent-encoded in
+// HTTP requests to the WebDAV server (RFC 3986 compliance).
+func TestReservedCharactersInPathAreEscaped(t *testing.T) {
+	var capturedPath string
+
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		capturedPath = r.RequestURI
+		// Return a 404 so the NewObject call fails cleanly
+		w.WriteHeader(http.StatusNotFound)
+	})
+	ts := httptest.NewServer(handler)
+	defer ts.Close()
+
+	configfile.Install()
+	m := configmap.Simple{
+		"type": "webdav",
+		"url":  ts.URL,
+	}
+
+	f, err := webdav.NewFs(context.Background(), remoteName, "", m)
+	require.NoError(t, err)
+
+	// Try to access a file with a semicolon in the name.
+	// We expect the request to fail (404), but the path should be escaped.
+	_, _ = f.NewObject(context.Background(), "my;test")
+
+	// The semicolon must be percent-encoded as %3B
+	assert.Contains(t, capturedPath, "my%3Btest", "semicolons in path should be percent-encoded")
+	assert.NotContains(t, capturedPath, "my;test", "raw semicolons should not appear in path")
+}