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.

1 files changed, 4 insertions, 5 deletions

diff --git a/premake5.lua b/premake5.lua
index d8a005d5..a1427cf3 100644
--- a/premake5.lua
+++ b/premake5.lua
@@ -33,12 +33,11 @@ workspace "Catch3"
     filter {}
 
 -- The Catch2-compatible engine, the Catch3 runner, property testing and
--- snapshots; the library is C++20, the engine's headers need only C++14 in
--- the code that includes them.
+-- snapshots; the library and the code that includes it need C++17.
 project "Catch3"
     kind "StaticLib"
     language "C++"
-    cppdialect "C++20"
+    cppdialect "C++17"
     targetdir "build/premake/bin/%{cfg.buildcfg}"
     objdir "build/premake/obj/Catch3/%{cfg.buildcfg}"
     files {
@@ -64,7 +63,7 @@ project "Catch3"
 project "Catch3WithMain"
     kind "StaticLib"
     language "C++"
-    cppdialect "C++14"
+    cppdialect "C++17"
     -- Visual Studio injects UNICODE for Windows projects, which would select
     -- Catch2's wmain entry point instead of the normal console main.
     defines { "DO_NOT_USE_WMAIN" }
@@ -77,7 +76,7 @@ project "Catch3WithMain"
 project "ProgmasoftPropertyTests"
     kind "ConsoleApp"
     language "C++"
-    cppdialect "C++20"
+    cppdialect "C++17"
     targetdir "build/premake/bin/%{cfg.buildcfg}"
     objdir "build/premake/obj/ProgmasoftPropertyTests/%{cfg.buildcfg}"
     files {