pkgtool.sh:pkgtoolp_mirror_fetch(): call pkg_fetch_download_clean_dlcache() post-{archive,Git} mirroring.
    pkgtool.sh:pkgtoolp_mirror_fetch(): mirror both archive as well as Git URL(s).
    subr/pkg_configure_patch.subr:pkg_configure_patch(): apply patches from within ${PKG_BASE_DIR} given both ${PKG_FNAME} and ${PKG_URLS_GIT}.
    subr.rtl/rtl_fetch.subr:rtl_fetch_mirror_urls_git(): ignore all but last component in ${_subdir}.
    subr.rtl/rtl_fetch.subr:rtl_fetch_mirror_urls_git(): create prerequisite directories.
    subr.rtl/rtl_fetch.subr:rtlp_fetch_url_git(): ignore all but last component in ${_subdir} wrt. ${_cache_dlname}.
    subr.rtl/rtl_fetch.subr:rtlp_fetch_url_git(): create prerequisite directories wrt. ${_tgtdir}.
    subr/ex_pkg_env.subr:exp_pkg_env_defaults(): reject absence of ${PKG_SUBDIR} given both ${PKG_FNAME} and ${PKG_URLS_GIT}.
    subr/pkg_fetch_download.subr:pkg_fetch_download_clean_dlcache(): initial implementation.
    subr/pkg_fetch_download.subr:pkg_fetch_download(): call pkg_fetch_download_clean_dlcache() post-{archive,Git} download.