Tags: patch

I have attached to this e-mail a patch that I believe fixes the bug, by
adding a condition that checks for the same conditions that
`delete-backward-char' uses for the same behavior, and delegates to
`delete-backward-char' if the conditions are met.

I have also found that the bug has another aspect, also fixed by the
patch. I will describe the steps for reproducing it below:

 1) emacs -Q
 2) C-q TAB w o r d
 3) C-SPC M-b
 4) Execute `backward-delete-char-untabify' (bound to DEL)

Notice that "word" was deleted, which is expected, but that the literal
TAB character was untabified, even though it was not necessary to do so.

The expected behavior is to delete "word" without untabifying.

I've looked at my previous e-mail and realized that I didn't leave clear
steps for reproduction for that aspect of the bug, so I will do so here:

 1) emacs -Q
 2) M-: (setq backward-delete-char-untabify-method 'hungry)
 3) SPC SPC w o r d
 4) C-SPC M-b
 5) Execute `backward-delete-char-untabify' (bound to DEL)

The expected behavior for it to delete "word", but instead it deletes
the two spaces to the left of point.

This patch fixes both issues with a single branch that makes it act like
`delete-backward-char' when it is appropriate to kill the region.