Say C++17 everywhere the project describes itselfchore/cpp17-descriptions

The move to C++17 left a trail of older claims. The Runner's own
.clang-format still said c++20; the result is byte for byte the same under
either value. Premake and Xmake still compiled the library as C++20 and
the main library as C++14, which meant their CI jobs were not testing the
language the project promises. Both now use C++17 for every target.

The rest is text: the Meson pkg-config description claimed C++14, comments
in the CMake and Meson files explained requirements that no longer exist,
.clang-tidy gave C++14 as the reason for two exclusions, issue templates
asked for C++20 samples, and the example headers named -std=c++14 and
catch2-with-main. The release notes and the migration guide state the
C++17 minimum. Doxygen's brief called the project "Catch2's test API",
which presents it as Catch2. Meson declared only BSL-1.0; it now names both
licenses of the tree. The amalgamated files are regenerated.

4 files changed, 6 insertions, 8 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 398260fd..aee8c7a3 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -396,8 +396,7 @@ set_target_properties(Catch3 PROPERTIES
   SOVERSION ${PROJECT_VERSION}
 )
 
-# Code that includes the engine's headers needs C++14, and the other
-# Progmasoft/ headers C++20; the library itself, with the runner, is built as C++20.
+# The library, and the code that includes its headers, need C++17.
 target_compile_features(Catch3 PUBLIC cxx_std_17)
 
 configure_file(
@@ -489,7 +488,7 @@ if(CATCH3_BUILD_EXAMPLES OR CATCH3_BUILD_EXTRA_TESTS)
       Catch3Pugixml
   )
   # These targets compile the library's sources themselves, the runner's
-  # among them, which need C++20.
+  # among them, which need C++17.
   target_compile_features(Catch3_buildall_interface INTERFACE cxx_std_17)
 endif()
 
diff --git a/src/Progmasoft/Catch3/Internal/Decomposer.hpp b/src/Progmasoft/Catch3/Internal/Decomposer.hpp
index 77a4a123..4c57d3be 100644
--- a/src/Progmasoft/Catch3/Internal/Decomposer.hpp
+++ b/src/Progmasoft/Catch3/Internal/Decomposer.hpp
@@ -128,7 +128,7 @@
 namespace Catch {
 
     namespace Detail {
-        // This was added in C++20, but we require only C++14 for now.
+        // This was added in C++20, but we require only C++17.
         template <typename T>
         using RemoveCVRef_t = std::remove_cv_t<std::remove_reference_t<T>>;
     }
diff --git a/src/Progmasoft/Catch3/meson.build b/src/Progmasoft/Catch3/meson.build
index b8d38908..7b75dc6d 100644
--- a/src/Progmasoft/Catch3/meson.build
+++ b/src/Progmasoft/Catch3/meson.build
@@ -347,8 +347,7 @@ if ((host_machine.system() == 'android') or
   catch3_dependencies += log_dep
 endif
 
-# Code that includes the engine's headers needs C++14, and the other
-# Progmasoft/ headers C++20; the library itself, with the runner, is built as C++20.
+# The library, and the code that includes its headers, need C++17.
 catch3 = static_library(
   'Catch3',
   sources,
@@ -368,7 +367,7 @@ if get_option('install')
   pkg.generate(
     catch3,
     filebase: 'catch3',
-    description: 'A C++ test framework with a Catch2-compatible API; headers need C++14 and above',
+    description: 'A C++ test framework with a Catch2-compatible API; headers need C++17 and above',
     url: 'https://github.com/Progmasoft/catch3',
   )
 endif
diff --git a/src/Progmasoft/Runner/.clang-format b/src/Progmasoft/Runner/.clang-format
index 1063b9ea..2cdf8220 100644
--- a/src/Progmasoft/Runner/.clang-format
+++ b/src/Progmasoft/Runner/.clang-format
@@ -1,7 +1,7 @@
 ---
 Language: Cpp
 BasedOnStyle: LLVM
-Standard: c++20
+Standard: c++17
 
 UseTab: Never
 IndentWidth: 4