update-kernel: Fix and improve -r logic

- Allow setting release in old (backward compatibility) format (release or
  version-release). This was broken since `@buildtime' is added (few
  years ago) to the `apt-cache pkgnames' output. Then it did not become
  better when `:disttag' is added to the output recently.

- Allow setting release in `uname -r' compatible format:
    version-flavour-release.

- Allow setting release in package name format, RPM style:
    [kernel-image-]flavour-[epoch:]version-release or APT style:
    [kernel-image-]flavour=[epoch:]version-release,
    [kernel-image-]flavour#[epoch:]version-release.
  This is for future `--list' option.

Fixes: Bug#39041.

update_kernel_modules_cetus.sh

@@ -34,7 +34,10 @@ Valid options are:
 	-i, --interactive interactive modules install
 	-f, -y, --force   force kernel upgrade
 	-t, --type        install kernel with specified flavour (ovz-smp, std-def, etc)
-	-r, --release     install kernel with specified release (alt10, alt22, etc)
+	-r, --release     desired kernel release (allowed formats by example:
+				old format: alt1, 5.7.19-alt1
+				classic kernel release: 5.7.19-std-def-alt1
+				package name: [kernel-image-]std-def-5.7.19-alt1)
 	-n, --dry-run     download packages, but don't install (--download-only)
 	-h, --help        show this text and exit
 EOF
@@ -103,10 +106,30 @@ else
 fi
 echo "Running kernel version: $current_kernel_pkgname"
 
-
-echo "Checking for available kernel packages..."
-# get list of all available kernel packages
-KERNEL_PKGS="$(apt-cache pkgnames kernel-image)"
+if [[ "$release" =~ ^[0-9]+\.[0-9.]+-.*-[^-]+$ ]]; then
+	# Rewrite release in `uname -r` compatible 'kernel release' format
+	ver="${release%-*}"
+	flv="${ver#*-}"
+	ver="${ver%%-*}"
+	rel="${release##*-}"
+	if [ -n "$kernel_flavour" ] && [ "$kernel_flavour" != "$flv" ]; then
+		fatal "Kernel flavour from '-t $kernel_flavour' does not match flavour from '-r' ($flv)."
+	fi
+	kernel_flavour="$flv"
+	release="$ver-$rel"
+	ver= flv= rel=
+elif [[ "$release" =~ ^(kernel-image-)?.*[-=#][0-9:]+\.[0-9.]+-[^-]+$ ]]; then
+	# Rewrite release in RPM, APT package format
+	ver="${release#kernel-image-}"
+	flv="${ver%[-=#]*-*}"
+	rel="${ver#$flv[-=#]}"
+	if [ -n "$kernel_flavour" ] && [ "$kernel_flavour" != "$flv" ]; then
+		fatal "Kernel flavour from '-t $kernel_flavour' does not match flavour from '-r' ($flv)."
+	fi
+	kernel_flavour="$flv"
+	release="$rel"
+	ver= flv= rel=
+fi
 
 # set kernel flavour. if not defined with -t option, use current
 current_kernel_flavour="$(uname -r)"
@@ -114,6 +137,10 @@ current_kernel_flavour="${current_kernel_flavour#*-}"
 current_kernel_flavour="${current_kernel_flavour%-*}"
 kernel_flavour="${kernel_flavour:-$current_kernel_flavour}"
 
+echo "Checking for available $kernel_flavour kernel packages..."
+# get list of all available kernel packages
+KERNEL_PKGS="$(apt-cache pkgnames "kernel-image-$kernel_flavour#" | sort -V)"
+
 # check that we have at least one kernel with defined kernel_flavour
 num_available_kernels="$(echo "$KERNEL_PKGS" | grep -c "$kernel_flavour")"
 [ "$num_available_kernels" != 0 ] || fatal "There are no available kernels with kernel flavour $kernel_flavour"
@@ -121,11 +148,11 @@ num_available_kernels="$(echo "$KERNEL_PKGS" | grep -c "$kernel_flavour")"
 # check that we have at least one kernel with defined kernel package release
 [ -z "$release" ] || {
 	num_available_kernels="$(echo "$KERNEL_PKGS" | grep -c "$release")"
-	[ "$num_available_kernels" != 0 ] || fatal "There are no available kernels with package release $release"
+	[ "$num_available_kernels" != 0 ] || fatal "There are no available $kernel_flavour kernels with package release $release"
 }
 
 # define how we must select available packages with needed flavour/release
-[ -z "$release" ] && pgkgrep="kernel-image-$kernel_flavour#" || pgkgrep="kernel-image-$kernel_flavour#.*$release$"
+[ -z "$release" ] && pgkgrep="kernel-image-$kernel_flavour#" || pgkgrep="kernel-image-$kernel_flavour#.*\b${release//./\\.}\([@:]\|\$\)"
 
 # get the maximum available kernel package version
 kmaxver=