Write the pending updates to a file for status bars

Each run saves the pending repo, AUR and kernel updates to
$XDG_STATE_HOME/update-notify/pending, independent of the threshold,
so a status bar can show them and drop the ones installed since.

README.md

@@ -69,6 +69,19 @@ Kernel versions are compared without `pkgrel`, so a stock packaging-only update
 
 The content of the last notification is stored in `$XDG_STATE_HOME/update-notify` (default `~/.local/state/update-notify`). Delete it to get the current notification again.
 
+## Status bars
+
+Each run also writes the pending updates to `$XDG_STATE_HOME/update-notify/pending`, whether or not the threshold is reached, for status bars such as xmobar to read:
+
+```
+threshold 30
+repo <pkg> <newver>
+aur <pkg> <newver>
+kernel <custom-pkg> <stock-ver>
+```
+
+The file reflects the last run. To keep a bar current after an upgrade, drop entries whose installed version (`pacman -Q`) is no longer older than `newver`, or, for `kernel` lines, whose custom build has caught up with `stock-ver` (ignoring `pkgrel`). This only reads local data, so it's cheap to run often.
+
 ## License
 
 GPL-3.0-or-later. See [LICENSE](LICENSE).

update-notify

@@ -93,20 +93,22 @@ if [[ -n $checkupdates_out ]]; then
 fi
 arch_updates=${#arch_list[@]}
 
-aur_updates=0
+aur_list=()
 if command -v aur >/dev/null 2>&1; then
     if aur_out=$(aur repo -u -d "$AUR_REPO"); then
-        [[ -n $aur_out ]] && aur_updates=$(wc -l <<< "$aur_out")
+        [[ -n $aur_out ]] && mapfile -t aur_list <<< "$aur_out"
     else
         echo "aur repo -u failed, AUR updates not counted" >&2
     fi
 fi
+aur_updates=${#aur_list[@]}
 updates=$((arch_updates + aur_updates))
 
 # ---------------------------------------------------------------------------
 # Kernel check: the stock kernel updated, but your custom build didn't
 # ---------------------------------------------------------------------------
 kernel_lines=()
+kernel_pending=()
 for stock_pkg in "${!KERNELS[@]}"; do
     custom_pkg=${KERNELS[$stock_pkg]}
 
@@ -120,9 +122,28 @@ for stock_pkg in "${!KERNELS[@]}"; do
     # pkgrel is ignored: a stock packaging-only bump doesn't need a rebuild.
     if (( $(vercmp "${stock_ver%-*}" "${custom_ver%-*}") > 0 )); then
         kernel_lines+=("Rebuild $custom_pkg ($stock_pkg $stock_ver)")
+        kernel_pending+=("$custom_pkg $stock_ver")
     fi
 done
 
+# ---------------------------------------------------------------------------
+# Pending list for status bars, one "<source> <pkg> <newver>" per line
+# ---------------------------------------------------------------------------
+{
+    printf 'threshold %s\n' "$THRESHOLD"
+    for item in "${arch_list[@]}"; do
+        read -r pkg _ _ new <<< "$item"
+        printf 'repo %s %s\n' "$pkg" "$new"
+    done
+    for item in "${aur_list[@]}"; do
+        read -r pkg _ _ new <<< "$item"
+        printf 'aur %s %s\n' "$pkg" "$new"
+    done
+    for item in "${kernel_pending[@]}"; do
+        printf 'kernel %s\n' "$item"
+    done
+} > "$state_dir/pending.tmp" && mv "$state_dir/pending.tmp" "$state_dir/pending"  # readers never see a partial file
+
 # ---------------------------------------------------------------------------
 # Build a single notification
 #   - kernel rebuild lines are always included