Add theme function

The theme function provides a quick but temporary switch to a specific
theme.

Themes can be applied with `styler theme [themename]`, they will be
instantly applied to all enabled applications. They will be lost on
restarts of the application or machine however.

Themes can be applied permanently with `styler set [themename]`, they
will be written into the application's settings. This *will* change
things in your local filesystem, so be wary. Generally, processors
should take the least invasive approach and use inclusion to append the
theme to the application's other settings.

But be *careful* with this option, and when in doubt double-check what
the processors you have installed do before losing your settings.

styler/.local/bin/styler

@@ -5,13 +5,16 @@ readonly BASE_PATH="${STYLER_DATA_PATH:-${XDG_DATA_HOME:-$HOME/.local/share}/sty
 readonly PACKAGE_PATH="$BASE_PATH/packages"
 readonly PROCESSOR_PATH="$BASE_PATH/processors"
 
-readonly VERSION="0.2.4"
+readonly VERSION="0.3.0"
 
 main() {
   local cmd=""
   local ret=0
 
   case "$1" in
+  -t | --theme | theme)
+    cmd="switch_theme"
+    ;;
   -s | --set | set)
     cmd="set_theme"
     ;;
@@ -46,7 +49,11 @@ usage() {
     "" \
     " Options:" \
     "" \
+    "     -t | theme      Temporarily switch theme. Use any valid base16 theme name (without base16- prefix)." \
+    "                     Theme will be lost upon restart, or application restarts." \
+    "" \
     "     -s | set        Set the theme. Use any valid base16 theme name (without base16- prefix)." \
+    "                     Same as 'theme' option, but changes will be made permanent." \
     "" \
     "     -d | download   Download a base16 template into the package directory or download a processor16" \
     "                     into the processor directory. Use user/repo format to automatically pull from github." \
@@ -105,8 +112,15 @@ get_themes() {
   echo "$themes" | sed "s/.*\\/base16-//" | sed "s/\\..*//" | sort | uniq
 }
 
+# temporarily switch theme, same thing as setting, only with permanence flag turned off for processors
+switch_theme() {
+  set_theme "$1" "false"
+}
+
+# call processors for all installed packages
 set_theme() {
   local theme="$1"
+  local permanent="${2:-true}"
 
   local packages
   packages="$(get_packages)"
@@ -134,7 +148,7 @@ set_theme() {
     # Compares application extension with existing processors and runs the appropriate processor if found
     processor=$(find "$PROCESSOR_PATH" -type f -name "theme_$appext")
     if [[ -f "$processor" ]]; then
-      "$processor" "$PACKAGE_PATH" "$pkg" "$theme"
+      "$processor" "$PACKAGE_PATH" "$pkg" "$theme" "$permanent"
     else
       printf "WARN: No processor found for application %s in %s. Make sure you install a processor for the application.\n" "$appext" "$PROCESSOR_PATH/" >&2
     fi