BUG: ediff-buffers does not consistently show "differences" or "difference regions" within the "active region"

[gnuist]

Hi.

BUG: ediff-buffers does not consistently show "difference regions"

You can try it yourself, 
make two small files A and B, where A has these two lines

a       b
c#d

and B as these two lines

a;b
c;d

and you can put an extra newline after each line and bunch of other lines so 
that when you run ediff-buffers, it hightlights only one line at a time as an 
active region.

You will immediately see that TAB is not highlighed in file A in its first 
line. This is *inconsistent* because in the second case c#d the hash is 
highlighted as the difference region within active region.

Just to be clear to any other newbie to this command, there are three type of 
highlighting in question.
1st is the highlighting of the entire active region or "selected difference 
region" which is the whole line.
2nd is the highlighting of the "differences" of "difference region" which is 
either TAB, semicolon or HASH, but not a b c d.
3rd is the highlighting of "unselected difference regions" which is usually 
SAME whitish color in both buffers.

Anyone at FSF/gnu to explain what appears to be such a basic bug staying there 
for so long?

Interestingly, when the hash in 2nd line is replaced by a TAB after making it 
active, it remains as a highlighted difference even if you cycle thru all the 
four highlighting modes.

Here is the punch line. Whatever the definition of highlighting, when I press 
"i" right after this to get the "status info", it says in the *ediff-message* 
buffer

Current difference number = 1
Showing regions that differ in white space & line breaks only
Selective browsing by regexp is off

What it means is that TAB and white space is being considered but is not being 
highlighted properly as HASH is being highlighted as the difference within the 
active region.

gnuist

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