Rewrite terminal auto-title

modules/helper/README.md

@@ -11,6 +11,8 @@ Functions
   - `is-autoloadable` checks if a file can be autoloaded by trying to load it
     in a subshell.
   - `is-callable` checks if a name is a command, function, or alias.
+  - `is-terminal-inside-multiplexer` checks if the currently running terminal is
+     inside a terminal multiplexer.
   - `is-true` checks a boolean variable for "true".
   - `coalesce` prints the first non-empty string in the arguments array.
 

modules/helper/init.zsh

@@ -21,6 +21,11 @@ function is-true {
   [[ -n "$1" && "$1" == (1|[Yy]([Ee][Ss]|)|[Tt]([Rr][Uu][Ee]|)|[Oo]([Nn]|)) ]]
 }
 
+# Checks if the currently running terminal is inside a terminal multiplexer.
+function is-terminal-inside-multiplexer {
+  [[ -n "$STY" || -n "$TMUX" || -n "$DVTM" ]]
+}
+
 # Prints the first non-empty string in the arguments array.
 function coalesce {
   for arg in $argv; do