CPack: why NOT reuse the installation tree?

Development
1

I am woundering why CPack waste the disk space in this way?

klein_cl:~/Workspace/cpp/axcioma/build$ tree -d -L 4 _CPack_Packages/
_CPack_Packages/
└── Linux
    ├── STGZ
    │   └── itaox11-2.2.0-Linux
    │       ├── bin
    │       ├── include
    │       ├── lib
    │       └── share
    ├── TGZ
    │   └── itaox11-2.2.0-Linux
    │       ├── bin
    │       ├── include
    │       ├── lib
    │       └── share
    └── TZ
        └── itaox11-2.2.0-Linux
            ├── bin
            ├── include
            ├── lib
            └── share

19 directories
klein_cl:~/Workspace/cpp/axcioma/build$ ls -lrsSa _CPack_Packages/Linux/*
_CPack_Packages/Linux/TZ:
total 29568
    4 drwxrwxr-x 6 klein_cl klein_cl     4096 Oct  5 13:16 itaox11-2.2.0-Linux
    4 drwxrwxr-x 5 klein_cl klein_cl     4096 Oct  5 13:16 ..
    4 drwxrwxr-x 3 klein_cl klein_cl     4096 Oct  5 13:16 .
29556 -rw-rw-r-- 1 klein_cl klein_cl 30262735 Oct  5 13:16 itaox11-2.2.0-Linux.tar.Z

_CPack_Packages/Linux/TGZ:
total 17556
    4 drwxrwxr-x 6 klein_cl klein_cl     4096 Oct  5 13:16 itaox11-2.2.0-Linux
    4 drwxrwxr-x 5 klein_cl klein_cl     4096 Oct  5 13:16 ..
    4 drwxrwxr-x 3 klein_cl klein_cl     4096 Oct  5 13:16 .
17544 -rw-rw-r-- 1 klein_cl klein_cl 17964304 Oct  5 13:16 itaox11-2.2.0-Linux.tar.gz

_CPack_Packages/Linux/STGZ:
total 17548
    4 drwxrwxr-x 6 klein_cl klein_cl     4096 Oct  5 13:16 itaox11-2.2.0-Linux
    4 drwxrwxr-x 5 klein_cl klein_cl     4096 Oct  5 13:16 ..
    4 drwxrwxr-x 3 klein_cl klein_cl     4096 Oct  5 13:16 .
17536 -rwxrwxrwx 1 klein_cl klein_cl 17953826 Oct  5 13:16 itaox11-2.2.0-Linux.sh
klein_cl:~/Workspace/cpp/axcioma/build$ ll
total 65676
drwxrwxr-x  8 klein_cl klein_cl     4096 Oct  5 13:16 ./
drwxrwxr-x 16 klein_cl klein_cl     4096 Oct  5 12:45 ../
-rw-rw-r--  1 klein_cl klein_cl    87128 Oct  5 12:45 .ninja_deps
-rw-rw-r--  1 klein_cl klein_cl     4674 Oct  5 12:45 .ninja_log
-rw-rw-r--  1 klein_cl klein_cl    28750 Oct  5 12:45 CMakeCache.txt
drwxrwxr-x  6 klein_cl klein_cl     4096 Oct  5 12:45 CMakeFiles/
drwxrwxr-x  2 klein_cl klein_cl     4096 Oct  5 12:45 CPM_modules/
-rw-rw-r--  1 klein_cl klein_cl     4055 Oct  5 12:45 CPackConfig.cmake
-rw-rw-r--  1 klein_cl klein_cl     4508 Oct  5 12:45 CPackSourceConfig.cmake
-rw-rw-r--  1 klein_cl klein_cl      374 Oct  5 12:45 CTestTestfile.cmake
drwxrwxr-x  3 klein_cl klein_cl     4096 Oct  5 12:45 _CPack_Packages/
drwxrwxr-x  5 klein_cl klein_cl     4096 Oct  5 12:45 _deps/
drwxrwxr-x  2 klein_cl klein_cl     4096 Oct  5 12:45 bin/
-rw-rw-r--  1 klein_cl klein_cl    70647 Oct  5 12:45 build.ninja
-rw-rw-r--  1 klein_cl klein_cl     7058 Oct  5 12:45 cmake_install.cmake
-rw-rw-r--  1 klein_cl klein_cl    15854 Oct  5 12:45 compile_commands.json
-rw-rw-r--  1 klein_cl klein_cl      499 Oct  5 12:45 cpm-package-lock.cmake
-rw-rw-r--  1 klein_cl klein_cl   772234 Oct  5 13:16 install_manifest.txt
-rwxrwxrwx  1 klein_cl klein_cl 17953826 Oct  5 13:16 itaox11-2.2.0-Linux.sh*
-rw-rw-r--  1 klein_cl klein_cl 30262735 Oct  5 13:16 itaox11-2.2.0-Linux.tar.Z
-rw-rw-r--  1 klein_cl klein_cl 17964304 Oct  5 13:16 itaox11-2.2.0-Linux.tar.gz
-rw-rw-r--  1 klein_cl klein_cl      283 Oct  5 12:45 itaox11Config.cmake
-rw-rw-r--  1 klein_cl klein_cl     2762 Oct  5 12:45 itaox11ConfigVersion.cmake
drwxrwxr-x  2 klein_cl klein_cl     4096 Oct  5 12:45 lib/
klein_cl:~/Workspace/cpp/axcioma/build$
2

CPack has no way of knowing that package format A is the same as package format B. For example, that directory should look far different for a macOS .pkg versus a .tar.X on macOS.

3

Technically I think it is also possible to have different contents for different package generators.