line editing malfunctions on deleting

[andrei caraman]

The incorrect behaviour occurs in xenial (gnuit 4.9.5-3build1), but not in trusty (gnuit 4.9.5-3). One way to demonstrate and/or reproduce the problem:

1. Start gitfm (for example in /tmp) with "gitfm /tmp"
2. Create file plata_edit.cgi with "> plata_edit.cgi"
3. Move the file cursor to this file
4. Try to rename the file to pmt_edit.cgi thus:
   4.1 Type "C-c R" for rename-file
   4.2 Type "C-a" to go to the beginning of the line, then right-arrow twice to move the cursor on letter l
   4.3 Press Del twice.

At this point the new name should be "pta_edit.cgi", but is "pta_edi..cgi". Further deletions (with Del or Backspace) make it even worse.

The same behaviour occurs when trying to change a file name on copy (F5) or move (F6). Also on editing a command line.

I'd be happy to provide more info to assist with diagnosis and hopefully fix.