[clang-doc] Fix use of source-root flag

[DiegoAstiazaran]

Summary

The value, if any, of --source-root flag was not being used.
This has been fixed and the logic was moved to the ClangDocContext contructor.

clang-tools-extra/clang-doc/Representation.cpp

 }
 
 ClangDocContext::ClangDocContext(tooling::ExecutionContext *ECtx,
                                  bool PublicOnly, StringRef OutDirectory,
                                  StringRef SourceRoot, StringRef RepositoryUrl,
                                  std::vector<std::string> UserStylesheets,
                                  std::vector<std::string> JsScripts)
     : ECtx(ECtx), PublicOnly(PublicOnly), OutDirectory(OutDirectory),
-      SourceRoot(SourceRoot), UserStylesheets(UserStylesheets),
-      JsScripts(JsScripts) {
+      UserStylesheets(UserStylesheets), JsScripts(JsScripts) {
+  llvm::SmallString<128> SourceRootDir(SourceRoot);
+  if (SourceRoot.empty())
+    // If no SourceRoot was provided the current path is used as the default
+    llvm::sys::fs::current_path(SourceRootDir);
+  this->SourceRoot = SourceRootDir.str();
   if (!RepositoryUrl.empty()) {
     this->RepositoryUrl = RepositoryUrl;
     if (!RepositoryUrl.empty() && RepositoryUrl.find("http://") != 0 &&
         RepositoryUrl.find("https://") != 0)
       this->RepositoryUrl->insert(0, "https://");
   }
 }
 
 } // namespace doc
 } // namespace clang

clang-tools-extra/clang-doc/tool/ClangDocMain.cpp

int main(int argc, const char **argv) {
 
   ArgumentsAdjuster ArgAdjuster;
   if (!DoxygenOnly)
     ArgAdjuster = combineAdjusters(
         getInsertArgumentAdjuster("-fparse-all-comments",
                                   tooling::ArgumentInsertPosition::END),
         ArgAdjuster);
 
-  llvm::SmallString<128> SourceRootDir;
-  // Check if the --source-root flag has a value
-  if (SourceRoot.empty())
-    // If it's empty the current path is used as the default
-    llvm::sys::fs::current_path(SourceRootDir);
-
   clang::doc::ClangDocContext CDCtx = {
       Exec->get()->getExecutionContext(),
       PublicOnly,
       OutDirectory,
-      SourceRootDir.str(),
+      SourceRoot,
       RepositoryUrl,
       {UserStylesheets.begin(), UserStylesheets.end()},
       {"index.js", "index_json.js"}};
 
   if (Format == "html") {
     void *MainAddr = (void *)(intptr_t)GetExecutablePath;
     std::string ClangDocPath = GetExecutablePath(argv[0], MainAddr);
     llvm::SmallString<128> AssetsPath;