Remove unnecessary local copies.

Use clang-tidy's performance-unnecessary-copy-initialization checker.
After applying the fix-its (which turns the copies into const&), revise
the changes and see whether the copies can be removed entirely by using
the original instead.

Source/CTest/cmCTestCoverageHandler.cxx

@@ -1356,7 +1356,6 @@ int cmCTestCoverageHandler::HandleLCovCoverage(
     return 0;
   }
   std::string testingDir = this->CTest->GetBinaryDir();
-  std::string tempDir = testingDir;
   std::string currentDirectory = cmSystemTools::GetCurrentWorkingDirectory();
 
   std::set<std::string> missingFiles;

Source/CTest/cmCTestSubmitCommand.cxx

@@ -219,12 +219,11 @@ bool cmCTestSubmitCommand::CheckArgumentValue(std::string const& arg)
   }
 
   if (this->ArgumentDoing == ArgumentDoingFiles) {
-    std::string filename(arg);
-    if (cmSystemTools::FileExists(filename.c_str())) {
-      this->Files.insert(filename);
+    if (cmSystemTools::FileExists(arg.c_str())) {
+      this->Files.insert(arg);
     } else {
       std::ostringstream e;
-      e << "File \"" << filename << "\" does not exist. Cannot submit "
+      e << "File \"" << arg << "\" does not exist. Cannot submit "
         << "a non-existent file.";
       this->Makefile->IssueMessage(cmake::FATAL_ERROR, e.str());
       this->ArgumentDoing = ArgumentDoingError;

Source/CTest/cmCTestUploadCommand.cxx

@@ -46,13 +46,12 @@ bool cmCTestUploadCommand::CheckArgumentKeyword(std::string const& arg)
 bool cmCTestUploadCommand::CheckArgumentValue(std::string const& arg)
 {
   if (this->ArgumentDoing == ArgumentDoingFiles) {
-    std::string filename(arg);
-    if (cmSystemTools::FileExists(filename.c_str())) {
-      this->Files.insert(filename);
+    if (cmSystemTools::FileExists(arg.c_str())) {
+      this->Files.insert(arg);
       return true;
     } else {
       std::ostringstream e;
-      e << "File \"" << filename << "\" does not exist. Cannot submit "
+      e << "File \"" << arg << "\" does not exist. Cannot submit "
         << "a non-existent file.";
       this->Makefile->IssueMessage(cmake::FATAL_ERROR, e.str());
       this->ArgumentDoing = ArgumentDoingError;

Source/cmExternalMakefileProjectGenerator.cxx

@@ -43,9 +43,8 @@ std::string cmExternalMakefileProjectGenerator::GetGlobalGeneratorName(
     return "";
   }
 
-  std::string currentName = fullName;
   // if we get only the short name, take the first global generator as default
-  if (currentName == this->GetName()) {
+  if (fullName == this->GetName()) {
     return this->SupportedGlobalGenerators[0];
   }
 
@@ -53,7 +52,7 @@ std::string cmExternalMakefileProjectGenerator::GetGlobalGeneratorName(
   for (std::vector<std::string>::const_iterator it =
          this->SupportedGlobalGenerators.begin();
        it != this->SupportedGlobalGenerators.end(); ++it) {
-    if (this->CreateFullGeneratorName(*it, this->GetName()) == currentName) {
+    if (this->CreateFullGeneratorName(*it, this->GetName()) == fullName) {
       return *it;
     }
   }

Source/cmGlobalNinjaGenerator.cxx

@@ -46,15 +46,14 @@ void cmGlobalNinjaGenerator::WriteComment(std::ostream& os,
   if (comment.empty())
     return;
 
-  std::string replace = comment;
   std::string::size_type lpos = 0;
   std::string::size_type rpos;
   os << "\n#############################################\n";
-  while ((rpos = replace.find('\n', lpos)) != std::string::npos) {
-    os << "# " << replace.substr(lpos, rpos - lpos) << "\n";
+  while ((rpos = comment.find('\n', lpos)) != std::string::npos) {
+    os << "# " << comment.substr(lpos, rpos - lpos) << "\n";
     lpos = rpos + 1;
   }
-  os << "# " << replace.substr(lpos) << "\n\n";
+  os << "# " << comment.substr(lpos) << "\n\n";
 }
 
 std::string cmGlobalNinjaGenerator::EncodeRuleName(std::string const& name)

Source/cmLocalGenerator.cxx

@@ -1766,13 +1766,12 @@ static void AddVisibilityCompileOption(std::string& flags,
                                        const std::string& lang,
                                        std::string* warnCMP0063)
 {
-  std::string l(lang);
-  std::string compileOption = "CMAKE_" + l + "_COMPILE_OPTIONS_VISIBILITY";
+  std::string compileOption = "CMAKE_" + lang + "_COMPILE_OPTIONS_VISIBILITY";
   const char* opt = lg->GetMakefile()->GetDefinition(compileOption);
   if (!opt) {
     return;
   }
-  std::string flagDefine = l + "_VISIBILITY_PRESET";
+  std::string flagDefine = lang + "_VISIBILITY_PRESET";
 
   const char* prop = target->GetProperty(flagDefine);
   if (!prop) {

Source/cmLocalUnixMakefileGenerator3.cxx

@@ -1178,10 +1178,9 @@ void cmLocalUnixMakefileGenerator3::AppendEcho(
 }
 
 std::string cmLocalUnixMakefileGenerator3::CreateMakeVariable(
-  const std::string& sin, const std::string& s2in)
+  const std::string& sin, const std::string& s2)
 {
   std::string s = sin;
-  std::string s2 = s2in;
   std::string unmodified = s;
   unmodified += s2;
   // if there is no restriction on the length of make variables

Source/cmMakefileTargetGenerator.cxx

@@ -294,7 +294,7 @@ void cmMakefileTargetGenerator::MacOSXContentGeneratorType::operator()(
     this->Generator->OSXBundleGenerator->InitMacOSXContentDirectory(pkgloc);
 
   // Get the input file location.
-  std::string input = source.GetFullPath();
+  std::string const& input = source.GetFullPath();
 
   // Get the output file location.
   std::string output = macdir;

Source/cmake.cxx

@@ -2296,10 +2296,8 @@ void displayMessage(cmake::MessageType t, std::ostringstream& msg)
 }
 
 void cmake::IssueMessage(cmake::MessageType t, std::string const& text,
-                         cmListFileBacktrace const& bt, bool force)
+                         cmListFileBacktrace const& backtrace, bool force)
 {
-  cmListFileBacktrace backtrace = bt;
-
   if (!force) {
     // override the message type, if needed, for warnings and errors
     cmake::MessageType override = this->ConvertMessageType(t);