clang-format: Allow fallback-style to take formatting arguments

[Chizi123]

Summary

Currently, -style is capable of accepting configuration options in its argument, while -fallback-style must be a predefined style.
This allows -fallback-style to take an argument formatted like a style argument.

[Chizi123]

Added a matching " to invalid fallback style

[Chizi123]

Accidentally added patch to commit

clang/lib/Format/Format.cpp

llvm::Expected<FormatStyle> getStyle(StringRef StyleName, StringRef FileName,
                                      StringRef Code, llvm::vfs::FileSystem *FS,
                                      bool AllowUnknownOptions) {
   if (!FS) {
     FS = llvm::vfs::getRealFileSystem().get();
   }
   FormatStyle Style = getLLVMStyle(guessLanguage(FileName, Code));
 
   FormatStyle FallbackStyle = getNoStyle();
-  if (!getPredefinedStyle(FallbackStyleName, Style.Language, &FallbackStyle))
-    return make_string_error("Invalid fallback style \"" + FallbackStyleName);
+  if (FallbackStyleName.startswith("{")) {
+    if (std::error_code ec = parseConfiguration(
+            FallbackStyleName, &FallbackStyle, AllowUnknownOptions))
+      return make_string_error("Error parsing -fallback-style: " +
+                               ec.message());
+  } else if (!getPredefinedStyle(FallbackStyleName, Style.Language,
+                                 &FallbackStyle)) {
+    return make_string_error("Invalid fallback style \"" + FallbackStyleName + "\"");
+  }
 
   if (StyleName.startswith("{")) {
     // Parse YAML/JSON style from the command line.
     if (std::error_code ec =
             parseConfiguration(StyleName, &Style, AllowUnknownOptions))
       return make_string_error("Error parsing -style: " + ec.message());
     return Style;
   }