Improve customization of source and work folders (#672)

* customization.cfg: add new entries for kernel paths

Two choices:
- Where to put git bare repository,
  - Will be implemented as a bare repository, the folder will have only
    compressed blobs and will be around ~400MB. Should be good to have
    even in HDDs
  - This is meant to be in a permanent storage like HDD or SSD.
    But some uses could have it on a tmpfs if the storage is very slow
    when compared to a full git (shallow) clone
- Where to have the work/build folder
  - This will be implemented through a git worktree,
    where the bare repo will be decompressed. This is best on a tmpfs folder
    but needs >=32GB for a full kernel build. Otherwise should be okay with
    modprobed-db

* customization.cfg: remove obsolete entries

the tmpfs related entries can be set with the previously added entries,
i.e. _kernel_work_folder and _kernel_source_folder

* prepare: check if obsoleted vars get set, warn if so and exit

Like this users will get notified about the change and act accordingly

* prepare: remove unused kernel subver patching code

this used to bump from kernel x.y to x.y.z

* prepare: add func to define kernel abs paths

We will use these absolute paths to refer to kernel folders (work and source)

* prepare: rewrite git fetching code

- Rename to "_setup_kernel_work_folder"
- Now we simply fetch directly the "commit hash" / "git tag"
  from the user chosen remote, no branches
- The source folder (the one that is preferably on disk) is only a bare repo
  with a small size (~400MB)
- The work folder is then (re)created / updated (as need) as a git worktree

* prepare: tkg_patcher: embed patch name into the message

Otherwise it doesn't work on the install.sh approach,
which reimplements a simple msg2 function that doesn't support %s
replacement

* PKGBUILD: use new path variable for work folder

* install.sh: use new path variable for work folder

* CI: setup source and build folder in /tmp

* prepare: update diffconfig with new kernel work folder var

install.sh

@@ -83,7 +83,7 @@ _install_dependencies() {
 
 if [ "$1" != "install" ] && [ "$1" != "config" ] && [ "$1" != "uninstall-help" ]; then
   msg2 "Argument not recognised, options are:
-        - config : interactive script that shallow clones the linux 5.x.y git tree into the folder linux-src-git, then applies extra patches and prepares the .config file
+        - config : interactive script that shallow clones the linux 5.x.y git tree into the folder \$_kernel_work_folder, then applies extra patches and prepares the .config file
                    by copying the one from the currently running linux system and updates it.
         - install : does the config step, proceeds to compile, then prompts to install
                     - 'DEB' distros: it creates .deb packages that will be installed then stored in the DEBS folder.
@@ -136,24 +136,9 @@ if [ "$1" = "install" ] || [ "$1" = "config" ]; then
     _distro=""
   fi
 
-  # cd into the linux-src folder is important before calling _tkg_srcprep
-  cd "$_where/linux-src-git"
   _tkg_srcprep
 
-  _build_dir="$_where"
-  if [ "$_use_tmpfs" = "true" ]; then
-    if [ -d "$_tmpfs_path/linux-tkg" ]; then
-      msg2 "Nuking linux-tkg tmpfs folder $_tmpfs_path/linux-tkg"
-      rm -rf "$_tmpfs_path/linux-tkg"
-    fi
-    mkdir "$_tmpfs_path/linux-tkg"
-    cp -r "$_where/linux-src-git" "$_tmpfs_path/linux-tkg/linux-src-git"
-
-    # cd into the linux-src folder is important before calling _tkg_srcprep
-    _build_dir="$_tmpfs_path/linux-tkg"
-    cd "$_tmpfs_path/linux-tkg/linux-src-git"
-  fi
-
+  _build_dir="$_kernel_work_folder_abs/.."
 
   # Uppercase characters are not allowed in source package name for debian based distros
   if [[ "$_distro" =~ ^(Debian|Ubuntu)$ && "$_cpusched" = "MuQSS" ]]; then
@@ -221,6 +206,8 @@ if [ "$1" = "install" ]; then
     #_runtime=$( time ( schedtool -B -n 1 -e ionice -n 1 "$@" 2>&1 ) 3>&1 1>&2 2>&3 ) || _runtime=$( time ( "$@" 2>&1 ) 3>&1 1>&2 2>&3 ) - Bash 5.2 is broken https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1018727
   #}
 
+  cd "$_kernel_work_folder_abs"
+
   if [[ "$_distro" =~ ^(Ubuntu|Debian)$ ]]; then
 
     msg2 "Building kernel DEB packages"
@@ -262,10 +249,7 @@ if [ "$1" = "install" ]; then
       _extra_ver_str="_${_kernel_flavor}"
     fi
 
-    _fedora_work_dir="${HOME}/.cache/linux-tkg-rpmbuild"
-    if [ "$_use_tmpfs" = "true" ]; then
-      _fedora_work_dir="$_tmpfs_path/linux-tkg/linux-tkg-rpmbuild"
-    fi
+    _fedora_work_dir="$_kernel_work_folder/linux-tkg-rpmbuild"
 
     msg2 "Building kernel RPM packages"
     RPMOPTS="--define '_topdir ${_fedora_work_dir}'" make ${llvm_opt} -j ${_thread_num} rpm-pkg EXTRAVERSION="${_extra_ver_str}"