[clang-format] Add a default format style that can be used by users of `getStyle`

Summary:
Tools that reformat code often call `getStyle` to decide the format style
to use on a certain source file. In practice, "file" style is widely used. As a
result, many tools hardcode "file" when calling `getStyle`, which makes it hard
to control the default style in tools across a codebase when needed. This change
introduces a `DefaultFormatStyle` constant (default to "file" in upstream), which
can be modified downstream if wanted, so that all users/tools built from the same
source tree can have a consistent default format style.

This also adds an DefaultFallbackStyle that is recommended to be used by tools and can be modified downstream.

Reviewers: sammccall, djasper

Reviewed By: sammccall

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D48492

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@335492 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/Format/Format.cpp b/lib/Format/Format.cpp
index 76dfc81950..374c25064a 100644
--- a/lib/Format/Format.cpp
+++ b/lib/Format/Format.cpp
@@ -2144,6 +2144,10 @@ FormatStyle::LanguageKind guessLanguage(StringRef FileName, StringRef Code) {
   return GuessedLanguage;
 }
 
+const char *DefaultFormatStyle = "file";
+
+const char *DefaultFallbackStyle = "LLVM";
+
 llvm::Expected<FormatStyle> getStyle(StringRef StyleName, StringRef FileName,
                                      StringRef FallbackStyleName,
                                      StringRef Code, vfs::FileSystem *FS) {