Move the filename on-top of the progress bar a little to the left to prevent filenames from being too long and bypassing the form's width.
Fix an issue where even when checking the 'Include all subdirectories', it would always only target the first subdirectory. This went in somehow by accident when I was trying to figure out an issue with merging directories that were too big (like a root disk containing a lot of files).
Get rid of some useless code which was useful only for a feature used in the past and enable the 'Merge' button everytime 'Stop' is pressed
Fix minor logic flaw which made the progress bar useless. The counter is now properly up-to-date with the filename we are showing.
If an exception is thrown when we try to read and write a file we also decrease the progress bar counter again.