Fix backup file path substitution

Previously, in a pattern like "{TIME:yy} {TIME}",
substituteBackupFilePath() would greedily use the entire string
"yy} {TIME" as the format specifier for the first TIME template, instead
of just "yy". Fix this, by adjusting the regular expression.

This ends up changing the behaviour of a weird corner case that is
covered in the tests, so change the test. I don't think anyone cares
about that case, and I think the current behaviour is better there.

Fixes keepassxreboot#10505 (proved by adding a test case very similar to what was
reported there).

src/core/Tools.cpp

@@ -449,33 +449,32 @@ namespace Tools
 
     QString substituteBackupFilePath(QString pattern, const QString& databasePath)
     {
-        // Fail if substitution fails
         if (databasePath.isEmpty()) {
             return {};
         }
 
-        // Replace backup pattern
-        QFileInfo dbFileInfo(databasePath);
-        QString baseName = dbFileInfo.completeBaseName();
+        const QString baseName = QFileInfo{databasePath}.completeBaseName();
 
-        pattern.replace(QString("{DB_FILENAME}"), baseName);
+        pattern.replace(QStringLiteral("{DB_FILENAME}"), baseName);
 
-        auto re = QRegularExpression(R"(\{TIME(?::([^\\]*))?\})");
+        const QDateTime now = Clock::currentDateTime();
+
+        const QRegularExpression re(R"(\{TIME(?::([^\\{}]*))?\})");
         auto match = re.match(pattern);
         while (match.hasMatch()) {
-            // Extract time format specifier
-            auto formatSpecifier = QString("dd_MM_yyyy_hh-mm-ss");
+            // Extract time format specifier, or use default value if absent
+            QString formatSpecifier = "dd_MM_yyyy_hh-mm-ss";
             if (!match.captured(1).isEmpty()) {
                 formatSpecifier = match.captured(1);
             }
-            auto replacement = Clock::currentDateTime().toString(formatSpecifier);
+            const auto replacement = now.toString(formatSpecifier);
             pattern.replace(match.capturedStart(), match.capturedLength(), replacement);
             match = re.match(pattern);
         }
 
         // Replace escaped braces
-        pattern.replace("\\{", "{");
-        pattern.replace("\\}", "}");
+        pattern.replace(QStringLiteral("\\{"), QStringLiteral("{"));
+        pattern.replace(QStringLiteral("\\}"), QStringLiteral("}"));
 
         return pattern;
     }

tests/TestTools.cpp

@@ -150,6 +150,12 @@ void TestTools::testBackupFilePatternSubstitution_data()
     QTest::newRow("Default time pattern (empty formatter)")
         << "{TIME:}" << DEFAULT_DB_FILE_PATH << DEFAULT_FORMATTED_TIME;
     QTest::newRow("Custom time pattern") << "{TIME:dd-ss}" << DEFAULT_DB_FILE_PATH << NOW.toString("dd-ss");
+    QTest::newRow("Time pattern twice") << "{TIME:yy} {TIME}" << DEFAULT_DB_FILE_PATH
+                                        << NOW.toString("yy") + QStringLiteral(" ") + DEFAULT_FORMATTED_TIME;
+    QTest::newRow("Complex custom time pattern")
+        << "./{TIME:yy}/{DB_FILENAME}_{TIME:yyyyMMdd_HHmmss}.old.kdbx" << DEFAULT_DB_FILE_PATH
+        << QStringLiteral("./") + NOW.toString("yy") + QStringLiteral("/") + DEFAULT_DB_FILE_NAME + QStringLiteral("_")
+               + NOW.toString("yyyyMMdd_HHmmss") + QStringLiteral(".old.kdbx");
     QTest::newRow("Invalid custom time pattern") << "{TIME:dd/-ss}" << DEFAULT_DB_FILE_PATH << NOW.toString("dd/-ss");
     QTest::newRow("Recursive substitution") << "{TIME:'{TIME}'}" << DEFAULT_DB_FILE_PATH << DEFAULT_FORMATTED_TIME;
     QTest::newRow("{DB_FILENAME} substitution")
@@ -161,7 +167,7 @@ void TestTools::testBackupFilePatternSubstitution_data()
     // Not relevant right now, added test anyway
     QTest::newRow("There should be no substitution loops") << "{DB_FILENAME}"
                                                            << "{TIME:'{DB_FILENAME}'}.ext"
-                                                           << "{DB_FILENAME}";
+                                                           << "{TIME:'{DB_FILENAME}'}";
 }
 
 void TestTools::testBackupFilePatternSubstitution()