ls: fix alignment when month names have varying widths

Reported by Samuel Thibault and Stéphane Raimbault, as the glibc fr_FR
locale has recently changed to use the official but variable width
abbreviated month names. Other glibc locales also have variable widths.
http://sourceware.org/ml/libc-locales/2008-q1/msg00035.html
http://sourceware.org/bugzilla/show_bug.cgi?id=9859
* NEWS: Mention the fix
* gl/lib/mbsalign.c: A new module to align and truncate a
string in a specified number of screen cells, while handling
multi-byte characters appropriately.
* gl/lib/mbsalign.h: Ditto
* gl/modules/mbsalign: Ditto
* bootstrap.conf: Reference the new module
* src/ls.c (abmon_init): New function, precompute the abbreviated
months aligned left in a minimum width column <= 5 screen cells.
(align_nstrftime): New function, replace the first %b in the
format specification to strftime with the precomputed month string.
Note using the cached month strings speeds up `ls -lU` by around 17%
on glibc-2.7-2 on linux at least.  Also if we implement this function
using heap storage rather than automatic storage, and use snprintf
instead of strcpy, ls will slow down by 2% and 1% respectively
(i.e. a net gain of 14% rather than 17%).
* tests/ls/abmon-align: A new test to test ls alignment for
various formats and locales
* tests/Makefile.am: Reference the new test

1 files changed, 4 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 1292896d6..7fdbd08cf 100644
--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,10 @@ GNU coreutils NEWS                                    -*- outline -*-
 
 * Noteworthy changes in release ?.? (????-??-??) [?]
 
+** Bug fixes
+
+  ls now aligns output correctly in the presence of abbreviated month
+  names from the locale database that have differing widths.
 
 * Noteworthy changes in release 7.2 (2009-03-31) [stable]