Add histmode on/off commands.

dotfiles/zshrc.d/history.zsh

@@ -0,0 +1,26 @@
+histmode() {
+  # This is very brittle as it assumes we're the only user of fc
+  case "$1" in
+    on)
+      if [ "$HISTDISABLED" -ne 1 ] ; then
+        echo "History is not disabled." >&2
+        return 1
+      fi
+      fc -P
+      HISTDISABLED=0
+      echo "History enabled."
+      ;;
+    off)
+      if [ "$HISTDISABLED" -eq 1 ] ; then
+        echo "History is already disabled." >&2
+        return 1
+      fi
+      HISTDISABLED=1
+      fc -p /dev/null $HISTSIZE 0
+      echo "History disabled."
+      ;;
+    *)
+      echo "Unknown command." >&2
+      ;;
+  esac
+}