CPack: allow custom file extension in archive generator

Help/cpack_gen/archive.rst

@@ -57,6 +57,12 @@ Variables specific to CPack Archive generator
   .. versionadded:: 3.9
     Per-component ``CPACK_ARCHIVE_<component>_FILE_NAME`` variables.
 
+.. variable:: CPACK_ARCHIVE_FILE_EXTENSION
+
+  .. versionadded:: 3.25
+
+  Package file extension. Default values are given in the list above.
+
 .. variable:: CPACK_ARCHIVE_COMPONENT_INSTALL
 
   Enable component packaging. If enabled (ON), then the archive generator

Help/release/dev/cpack-archive-custom-extension.rst

@@ -0,0 +1,6 @@
+cpack-archive-custom-extension
+------------------------------
+
+* The :cpack_gen:`CPack Archive Generator` gained a new
+  :variable:`CPACK_ARCHIVE_FILE_EXTENSION` variable to control
+  the package file name extension.

Source/CPack/cmCPackArchiveGenerator.cxx

@@ -94,6 +94,18 @@ std::string cmCPackArchiveGenerator::GetArchiveComponentFileName(
 int cmCPackArchiveGenerator::InitializeInternal()
 {
   this->SetOptionIfNotSet("CPACK_INCLUDE_TOPLEVEL_DIRECTORY", "1");
+  cmValue newExtensionValue = this->GetOption("CPACK_ARCHIVE_FILE_EXTENSION");
+  if (!newExtensionValue.IsEmpty()) {
+    std::string newExtension = *newExtensionValue;
+    if (!cmHasLiteralPrefix(newExtension, ".")) {
+      newExtension = cmStrCat('.', newExtension);
+    }
+    cmCPackLogger(cmCPackLog::LOG_DEBUG,
+                  "Using user-provided file extension "
+                    << newExtension << " instead of the default "
+                    << this->OutputExtension << std::endl);
+    this->OutputExtension = std::move(newExtension);
+  }
   return this->Superclass::InitializeInternal();
 }