Help users download from custom sources

Describe in the README how to support downloading from a custom source, and
add a source code location for examples.

3 files changed, 116 insertions, 1 deletions

diff --git a/README.md b/README.md
index f626dd1..a0aebad 100644
--- a/README.md
+++ b/README.md
@@ -105,6 +105,32 @@ chmod +x /usr/local/sbin/install-kernel
 
 ## Source
 
+### Customizing Update Downloads
+
+You can add a section to the [script](src/slack-autoupdate) to pull updates
+using different tools or sources.  The sections use the following structure,
+and some examples are provided in the [recipes](src/recipes) directory.
+
+```
+if ! OUTPUT="$(
+  # Redirect error output to standard output.
+  exec 2>&1
+
+  # Download updates into $STAGING_DIR.
+  #
+  # On failure the command output is appended to the error file.
+  # Update information should be appended to the $UPDATE_INFO file.
+
+)"; then
+  if [ -f "$UPDATE_ERROR" ]; then
+    >>"$UPDATE_ERROR" echo ""
+    >>"$UPDATE_ERROR" echo ""
+  fi
+
+  >>"$UPDATE_ERROR" echo -e "[Update Name]:\n\n$OUTPUT"
+fi
+```
+
 ### Testing
 
 You can test the project by running the shell files under the 'test' folder.
diff --git a/src/recipes/use-current-kernel.sh b/src/recipes/use-current-kernel.sh
new file mode 100644
index 0000000..2b82a25
--- /dev/null
+++ b/src/recipes/use-current-kernel.sh
@@ -0,0 +1,89 @@
+# Download kernel updates from Slackware Current for a stable release.
+#
+# For this to work, make sure the kernel packages are blacklisted in
+# /etc/slackpkg/blacklist.
+#
+#  kernel-generic.*
+#  kernel-huge.*
+#  kernel-modules.*
+#  kernel-source.*
+#
+# This script uses an unusual pattern for running commands on exit, similar to
+# Golang's defer.  These will not be run when the script is stopped with
+# Control+c.
+#
+# D="[command]; $D"; trap "$D" EXIT
+#
+
+echo "Checking kernel updates from Slackware Current (slackpkg)..."
+
+# Get Slackware version.
+source /etc/os-release
+
+SOURCE=$(sed -n '
+        # Remove leading and trailing blanks
+        s/^[[:blank:]]*//
+        s/[[:blank:]]*$//
+        # Only one token is allowed per line
+        /[[:blank:]]/d
+        # A single solidus should end the URI
+        s,[/]*$,/,
+        # Print the lines beginning with one of the URI schemes we look for
+        \@^file://@p
+        \@^cdrom://@p
+        \@^local://@p
+        \@^https\{0,1\}://@p
+        \@^ftps\{0,1\}://@p' /etc/slackpkg/mirrors)
+SOURCE="$(echo $SOURCE | sed 's/-$VERSION/-current/')"
+
+yes y | slackpkg -mirror="$SOURCE" -batch=on -default_answer=yes update
+D="yes | slackpkg -batch=on -default_answer=yes update"; trap "$D" EXIT
+
+PACKAGE_UPDATES="$(mktemp /tmp/slack-autoupdate.XXXXXX)"
+D="rm -f ${PACKAGE_UPDATES}; $D"; trap "$D" EXIT
+
+mv /etc/slackpkg/blacklist /etc/slackpkg/blacklist.orig
+touch /etc/slackpkg/blacklist
+D="mv -f /etc/slackpkg/blacklist.orig /etc/slackpkg/blacklist; $D"; trap "$D" EXIT
+
+slackpkg -batch=on -default_answer=n \
+  upgrade kernel \
+  | grep "\.t.z$" \
+  | tee "$PACKAGE_UPDATES"  \
+  || exit "$?"
+
+if [ ! -s "$PACKAGE_UPDATES" ]; then
+  # No updates
+  exit 0
+fi
+
+while read PKG; do
+  PKG_URL="$(
+    grep "${PKG}$" /var/lib/slackpkg/CHECKSUMS.md5 \
+      | tr -s ' ' \
+      | cut -f 2 -d ' '
+    )" || exit "$?"
+
+  wget \
+    --directory-prefix="$STAGING_DIR" \
+    "${SOURCE}${PKG_URL}" \
+    "${SOURCE}${PKG_URL}.asc" \
+    || exit 1
+done <"$PACKAGE_UPDATES"
+
+if ! gpg2 --verify-files "$STAGING_DIR"/kernel-*.asc; then
+  echo "gpg verification failed"
+  exit 1
+fi
+
+(
+  # Redirect this subshell's standard output to info file.
+  exec 1>>"$UPDATE_INFO"
+
+  echo "## Slackware current kernel updates"
+  echo
+  while read PKG; do
+    echo " - $PKG"
+  done <"$PACKAGE_UPDATES"
+  echo
+)
diff --git a/src/slack-autoupdate b/src/slack-autoupdate
index 78501a8..250c678 100644
--- a/src/slack-autoupdate
+++ b/src/slack-autoupdate
@@ -64,7 +64,7 @@ if ! OUTPUT="$(
 
   echo "Checking updates for slackpkg..."
 
-  slackpkg -batch=on -default_answer=n update || exit "$?"
+  yes | slackpkg -batch=on -default_answer=yes update || exit "$?"
 
   CHANGELOG_TXT="$(mktemp /tmp/slack-autoupdate.XXXXXX)"
   PACKAGE_UPDATES="$(mktemp /tmp/slack-autoupdate.XXXXXX)"