`header_template` source kind is a header file with a `.config` on its stem

src/dds/source/file.cpp

     auto ext_found
         = std::lower_bound(header_exts.begin(), header_exts.end(), p.extension(), std::less<>());
     if (ext_found != header_exts.end() && *ext_found == p.extension()) {
+        auto stem = p.stem();
+        if (stem.extension() == ".config") {
+            return source_kind::header_template;
+        }
         return source_kind::header;
     }
 
         return std::nullopt;
     }
 
-    if (ends_with(p.stem().string(), ".test")) {
+    if (p.stem().extension() == ".test") {
         return source_kind::test;
     }
 
-    if (ends_with(p.stem().string(), ".main")) {
+    if (p.stem().extension() == ".main") {
         return source_kind::app;
     }
 

src/dds/source/file.hpp

 
 enum class source_kind {
     header,
+    header_template,
     source,
     test,
     app,

src/dds/source/file.test.cpp

+#include <dds/source/file.hpp>
+
+#include <catch2/catch.hpp>
+
+using dds::source_kind;
+
+TEST_CASE("Infer source kind") {
+    using dds::infer_source_kind;
+    auto k = infer_source_kind("foo.h");
+    CHECK(k == source_kind::header);
+    CHECK(infer_source_kind("foo.hpp") == source_kind::header);
+    CHECK_FALSE(infer_source_kind("foo.txt"));  // Not a source file extension
+
+    CHECK(infer_source_kind("foo.hh") == source_kind::header);
+    CHECK(infer_source_kind("foo.config.hpp") == source_kind::header_template);
+}