[FS#634] Factory flashing fails because LEDE filename is too long (>= 64 chars)

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Baptiste Jonglez (bjonglez) 

Attached to Project - LEDE Project
Summary - Factory flashing fails because LEDE filename is too long (>= 64 chars)
Task Type - Bug Report
Category - Base system
Status - New
Assigned To - 
Operating System - All
Severity - Medium
Priority - Medium
Reported Version - All
Due in Version - Undecided
Due Date - Undecided
Details - On a TP-Link TL-WR841N v11, flashing LEDE from the web interface of the stock firmware is not possible.

This is caused by a stupid check that refuses filename longer than 64 chars in the web interface.  The check is implemented in javascript and returns a cryptic error message like "Please select a file to upload", as if no file was selected.

The current naming scheme is quite long:

$ echo 'lede-17.01.0-r3205-59508e3-ar71xx-generic-tl-wr841-v11-squashfs-factory-eu.bin' | wc -c
79

Shortening the name like the following would decrease the length below 64 chars, and leave some space for a custom suffix (e.g. using EXTRA_IMAGE_NAME in the Imagebuilder):

$ echo 'lede-17.01.0-ar71xx-tlwr841v11-squashfs-factory-eu.bin' | wc -c
55

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=634