cat-highlight: Add support for CATOPEN; add example

.config/zsh/functions/cat-highlight

@@ -1,17 +1,27 @@
 #!/usr/bin/env zsh
-# Highlight cat output with whatever less is using for highlighting. The command
-# in $LESSOPEN needs to be able to work with multiple files.
+# Highlight cat output with either $CATOPEN or $LESSOPEN. The command needs to
+# have %s in it that will be replaced with all input files. Some programs that
+# are known to not work will be ignored in $LESSOPEN but not in $CATOPEN.
 
-# Check if we are in a terminal and $LESSOPEN is not empty
-if [[ -t 1 && -n "${LESSOPEN}" ]]; then
-    # Programs that won't work with cat
-    local -a known_bad=("lesspipe")
-    for baddy in ${known_bad}; do
-        if [[ "${LESSOPEN}" =~ "${baddy}" ]]; then
-            \cat "${@}"
-            return ${?}
-        fi
-    done
+# Example:
+# export CATOPEN="highlight --force --out-format=truecolor --stdout %s"
+# alias cat='cat-highlight'
+
+# Check if we are in a terminal and a highlighter is defined
+if [[ -t 1 ]] && [[ -n "${CATOPEN}" || -n "${LESSOPEN}" ]]; then
+    if [[ -z "${CATOPEN}" ]]; then
+        # Programs that won't work with cat
+        local -a known_bad=("lesspipe")
+        for baddy in ${known_bad}; do
+            if [[ "${LESSOPEN}" =~ "${baddy}" ]]; then
+                \cat "${@}"
+                return ${?}
+            fi
+        done
+        local catopen="${LESSOPEN/|/}"
+    else
+        local catopen="${CATOPEN}"
+    fi
 
     local -a args
     local -a files
@@ -24,7 +34,6 @@ if [[ -t 1 && -n "${LESSOPEN}" ]]; then
         fi
     done
 
-    local catopen="${LESSOPEN/|/}"
     eval "${catopen/\%s/${files}} | \cat ${args}"
 else
     \cat "${@}"