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

customization.cfg

@@ -23,6 +23,18 @@ _NUKR="true"
 # Git mirror to use to get the kernel sources, possible values are "kernel.org", "googlesource.com", "github.com" and "torvalds"
 _git_mirror="kernel.org"
 
+# Folder where to checkout the kernel sources and build inside it
+# Note: - Start with a '/' for an absolute path
+#       - This setting can be used to set the work/build folder to a tmpfs folder
+#         - Requires >= 32GB ram when building a full kernel, should work with less ram with modprobed-db
+_kernel_work_folder="linux-src-git"
+
+# Permanent folder where to keep the git clone and fetch new blobs
+# Note: - Start with a '/' for an absolute path
+#       - If your internet is faster than your storage, it may be wise to put this folder
+#         in a tmpfs location (although it will reclone after each restart / tmpfs folder cleanup)
+_kernel_source_folder="linux-kernel.git"
+
 # Custom compiler root dirs - Leave empty to use system compilers
 # Example: CUSTOM_GCC_PATH="/home/frog/PKGBUILDS/mostlyportable-gcc/gcc-mostlyportable-9.2.0"
 CUSTOM_GCC_PATH=""
@@ -54,17 +66,6 @@ _diffconfig=""
 # Set to the file name where the generated config fragment should be written to. Only used if _diffconfig is active.
 _diffconfig_name=""
 
-# [install.sh specific] Use tmpfs as a work directory, recommended when RAM >= 32GB to reduce HDD/SSD usage. For more information, see https://wiki.archlinux.org/title/Tmpfs
-_use_tmpfs="false"
-
-# Always make a fresh clone of the source in tmpfs to speed up compilation times
-# ! This will take ~20GB of RAM by itself, so don't use on <32GB RAM systems !
-_source_in_tmpfs="false"
-
-# [install.sh specific] tmpfs folder path, only used when _use_tmpfs="true".
-#                       Creates a linux-tkg work folder within that pathmake sure to have nothing important in "$_tmpfs_path/linux-tkg"
-_tmpfs_path="/tmp"
-
 # [install.sh: Generic and Gentoo specific] Dracut options when generating initramfs
 _dracut_options="--lz4"