erc-track-shorten-function is a variable defined in `erc-track.el'.
Its value is
erc-track-shorten-names
This variable may be risky if used as a file-local variable.
Documentation:
This function will be used to reduce the channel names before display.
It takes one argument, CHANNEL-NAMES which is a list of strings.
It should return a list of strings of the same number of elements.
If nil instead of a function, shortening is disabled.
You can customize this variable.