* function, as all the arguments to wfShellExec can become unwieldy.
*
* @note This also includes errors from limit.sh, e.g. if $wgMaxShellFileSize is exceeded.
- * @param string $cmd Command line, properly escaped for shell.
+ * @param string|string[] $cmd If string, a properly shell-escaped command line,
+ * or an array of unescaped arguments, in which case each value will be escaped
+ * Example: [ 'convert', '-font', 'font name' ] would produce "'convert' '-font' 'font name'"
* @param null|mixed &$retval Optional, will receive the program's exit code.
* (non-zero is usually failure)
* @param array $environ Optional environment variables which should be