doc: pretty-formats describe use of ellipsis in truncation

Commit a7f01c6 (pretty: support truncating in %>, %< and %><,
2013-04-19) added the use of ellipsis when truncating placeholder
values.

Show our 'two dot' ellipsis, and examples for the left, middle and
right truncation to avoid any confusion as to which end of the string
is adjusted. (cf justification and sub-string).

Signed-off-by: Philip Oakley <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: PhilipOakley

Documentation/pretty-formats.txt

@@ -149,9 +149,9 @@ The placeholders are:
 '%<( <N> [,trunc|ltrunc|mtrunc])':: make the next placeholder take at
 				  least N column widths, padding spaces on
 				  the right if necessary.  Optionally
-				  truncate at the beginning (ltrunc),
-				  the middle (mtrunc) or the end
-				  (trunc) if the output is longer than
+				  truncate (with ellipsis '..') at the left (ltrunc) `..ft`,
+				  the middle (mtrunc) `mi..le`, or the end
+				  (trunc) `rig..`, if the output is longer than
 				  N columns.
 				  Note 1: that truncating
 				  only works correctly with N >= 2.