execute_process: Allow UTF-8 as a synonym for the UTF8 keyword

UTF-8 is the proper naming according to the UTF-8 RFC and is also the
name used for a similar keyword in the file() command. This commit
brings (backward compatible) consistency to the keyword names and allows
the standard UTF-8 name to be used with execute_process(). The old UTF8
keyword is still supported.

Help/command/execute_process.rst

@@ -90,8 +90,10 @@ Options:
    Use the ANSI codepage.
  ``OEM``
    Use the original equipment manufacturer (OEM) code page.
- ``UTF8``
-   Use the UTF-8 codepage.
+ ``UTF8`` or ``UTF-8``
+   Use the UTF-8 codepage. Prior to CMake 3.11.0, only ``UTF8`` was accepted
+   for this encoding. In CMake 3.11.0, ``UTF-8`` was added for consistency with
+   the `UTF-8 RFC <https://www.ietf.org/rfc/rfc3629>`_ naming convention.
 
 If more than one ``OUTPUT_*`` or ``ERROR_*`` option is given for the
 same pipe the precedence is not specified.

Source/cmProcessOutput.cxx

@@ -13,7 +13,7 @@ cmProcessOutput::Encoding cmProcessOutput::FindEncoding(
   std::string const& name)
 {
   Encoding encoding = Auto;
-  if (name == "UTF8") {
+  if ((name == "UTF8") || (name == "UTF-8")) {
     encoding = UTF8;
   } else if (name == "NONE") {
     encoding = None;

Tests/CMakeLib/testEncoding.cxx

@@ -31,7 +31,7 @@ int main(int argc, char* argv[])
   }
   const std::string encoding(argv[1]);
 #ifdef _WIN32
-  if (encoding == "UTF8") {
+  if ((encoding == "UTF8") || (encoding == "UTF-8")) {
     setEncoding(consoleOut, CP_UTF8);
   } else if (encoding == "ANSI") {
     setEncoding(consoleOut, CP_ACP);

Tests/RunCMake/execute_process/EncodingUTF-8-stderr.txt

@@ -0,0 +1 @@
+यूनिकोड είναι very здорово!

Tests/RunCMake/execute_process/RunCMakeTest.cmake

@@ -10,6 +10,7 @@ run_cmake_command(MergeOutputVars ${CMAKE_COMMAND} -P ${RunCMake_SOURCE_DIR}/Mer
 run_cmake(EncodingMissing)
 if(TEST_ENCODING_EXE)
   run_cmake_command(EncodingUTF8 ${CMAKE_COMMAND} -DTEST_ENCODING=UTF8 -DTEST_ENCODING_EXE=${TEST_ENCODING_EXE} -P ${RunCMake_SOURCE_DIR}/Encoding.cmake)
+  run_cmake_command(EncodingUTF-8 ${CMAKE_COMMAND} -DTEST_ENCODING=UTF-8 -DTEST_ENCODING_EXE=${TEST_ENCODING_EXE} -P ${RunCMake_SOURCE_DIR}/Encoding.cmake)
 endif()
 
 if(EXIT_CODE_EXE)