cmake: tar: Display warning when no files provided during archive creation

Source/cmcmd.cxx

@@ -1114,6 +1114,10 @@ int cmcmd::ExecuteCMakeCommand(std::vector<std::string>& args)
           return 1;
         }
       } else if (flags.find_first_of('c') != std::string::npos) {
+        if (files.empty()) {
+          cmSystemTools::Message("tar: No files or directories specified",
+                                 "Warning");
+        }
         if (!cmSystemTools::CreateTar(outFile.c_str(), files, compress,
                                       verbose, mtime, format)) {
           cmSystemTools::Error("Problem creating tar: " + outFile);

Tests/RunCMake/CommandLineTar/RunCMakeTest.cmake

@@ -4,6 +4,7 @@ function(external_command_test NAME)
   run_cmake_command(${NAME} ${CMAKE_COMMAND} -E ${ARGN})
 endfunction()
 
+external_command_test(without-files tar cvf bad.tar)
 external_command_test(bad-opt1   tar cvf bad.tar --bad)
 external_command_test(bad-mtime1 tar cvf bad.tar --mtime=bad .)
 external_command_test(bad-from1  tar cvf bad.tar --files-from=bad)
@@ -13,10 +14,10 @@ external_command_test(bad-from4  tar cvf bad.tar --files-from=${CMAKE_CURRENT_LI
 external_command_test(bad-from5  tar cvf bad.tar --files-from=${CMAKE_CURRENT_LIST_DIR}/bad-from5.txt)
 external_command_test(end-opt1   tar cvf bad.tar -- --bad)
 external_command_test(end-opt2   tar cvf bad.tar --)
-external_command_test(mtime      tar cvf bad.tar "--mtime=1970-01-01 00:00:00 UTC")
-external_command_test(bad-format tar cvf bad.tar "--format=bad-format")
-external_command_test(zip-bz2    tar cvjf bad.tar "--format=zip")
-external_command_test(7zip-gz    tar cvzf bad.tar "--format=7zip")
+external_command_test(mtime      tar cvf bad.tar "--mtime=1970-01-01 00:00:00 UTC" .)
+external_command_test(bad-format tar cvf bad.tar "--format=bad-format" .)
+external_command_test(zip-bz2    tar cvjf bad.tar "--format=zip" .)
+external_command_test(7zip-gz    tar cvzf bad.tar "--format=7zip" .)
 
 run_cmake(7zip)
 run_cmake(gnutar)

Tests/RunCMake/CommandLineTar/end-opt2-stderr.txt

@@ -0,0 +1 @@
+^tar: No files or directories specified

Tests/RunCMake/CommandLineTar/without-files-stderr.txt

@@ -0,0 +1 @@
+^tar: No files or directories specified