Hi,
I was wondering why I sended patches that do not improve
anything. After some more investigation I found out again what the
patches improve:

The source is repacked by guix and the patches applied before the source
is stored in the store.  With the current guix:

┌────
│ ~/src/guix/build$ tar -tf `guix build -S emacs-clang-format`
│ cfe-6.0.1.src/
│ cfe-6.0.1.src/.arcconfig
│ cfe-6.0.1.src/.clang-format
│ cfe-6.0.1.src/.clang-tidy
│ cfe-6.0.1.src/.gitignore
│ cfe-6.0.1.src/CMakeLists.txt
│ cfe-6.0.1.src/CODE_OWNERS.TXT
│ cfe-6.0.1.src/INPUTS/
│ cfe-6.0.1.src/INPUTS/Cocoa_h.m
│ cfe-6.0.1.src/INPUTS/all-std-headers.cpp
│ cfe-6.0.1.src/INPUTS/c99-intconst-1.c
│ cfe-6.0.1.src/INPUTS/carbon_h.c
│ cfe-6.0.1.src/INPUTS/cfg-big-switch.c
│ cfe-6.0.1.src/INPUTS/cfg-long-chain1.c
│ cfe-6.0.1.src/INPUTS/cfg-long-chain2.c
│ cfe-6.0.1.src/INPUTS/cfg-long-chain3.c
│ cfe-6.0.1.src/INPUTS/cfg-nested-switches.c
│ cfe-6.0.1.src/INPUTS/cfg-nested-var-scopes.cpp
│ cfe-6.0.1.src/INPUTS/iostream.cc
│ cfe-6.0.1.src/INPUTS/macro_pounder_fn.c
│ cfe-6.0.1.src/INPUTS/macro_pounder_obj.c
│ cfe-6.0.1.src/INPUTS/stpcpy-test.c
│ cfe-6.0.1.src/INSTALL.txt
│ cfe-6.0.1.src/LICENSE.TXT
│ cfe-6.0.1.src/ModuleInfo.txt
│ cfe-6.0.1.src/NOTES.txt
│ ... < the rest of clangs sources >
└────

With the patches applied:

┌────
│ ~/src/guix/build$ tar -tf `guix build -S emacs-clang-format`
│ ... < repacking and building the source>
│ successfully built
/gnu/store/yds0n90idgaa65ladnpbcdjkqgs8l61d-emacs-clang-format-6.0.1.tar.xz.drv
│ cfe-6.0.1.src/
│ cfe-6.0.1.src/clang-format.el
└────

So it does save disk space. I also think that these sources can be
substituted (This may still not be the case though).  The term source
derivation is mentioned in the description of guix builds `-S` option.

I would argue that I implement the file deletion in the source snippet
in package-elisp-from-package. I hope this makes clear what the purpose
of the first two patches is.

Tim.