Adds support for auto-detection of compilation databases
from a source file and changes clang-check to make use of this.

This makes clang-check just work on in-tree builds, and allows
easy setup via a symlink per source directory to make clang-check
work without any extra configuration.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@159990 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/clang-check/ClangCheck.cpp b/tools/clang-check/ClangCheck.cpp
index d68e282..ef4a3ac 100644
--- a/tools/clang-check/ClangCheck.cpp
+++ b/tools/clang-check/ClangCheck.cpp
@@ -42,8 +42,9 @@
 using namespace llvm;
 
 cl::opt<std::string> BuildPath(
-  cl::Positional,
-  cl::desc("<build-path>"));
+  "p",
+  cl::desc("<build-path>"),
+  cl::Optional);
 
 cl::list<std::string> SourcePaths(
   cl::Positional,
@@ -56,8 +57,13 @@
   cl::ParseCommandLineOptions(argc, argv);
   if (!Compilations) {
     std::string ErrorMessage;
-    Compilations.reset(CompilationDatabase::loadFromDirectory(BuildPath,
-                                                              ErrorMessage));
+    if (!BuildPath.empty()) {
+      Compilations.reset(CompilationDatabase::loadFromDirectory(BuildPath,
+                                                                ErrorMessage));
+    } else {
+      Compilations.reset(CompilationDatabase::autoDetectFromSource(
+          SourcePaths[0], ErrorMessage));
+    }
     if (!Compilations)
       llvm::report_fatal_error(ErrorMessage);
   }