progress: use 'encoding.trim' to trim items in output line correctly

Before this patch, 'progress' extension trims items in output line by
directly slicing byte sequence, but it may split at intermediate
multi-byte sequence.

This patch uses 'encoding.trim' to trim items in output line
correctly, even if it contains multi-byte characters.

hgext/progress.py

@@ -139,9 +139,9 b' class progbar(object):'
                 else:
                     wid = 20
                 if slice == 'end':
-                    add = item[-wid:]
+                    add = encoding.trim(item, wid, leftside=True)
                 else:
-                    add = item[:wid]
+                    add = encoding.trim(item, wid)
                 add += (wid - len(add)) * ' '
             elif indicator == 'bar':
                 add = ''

tests/test-progress.t

@@ -33,7 +33,7 b''
   >     loops = abs(loops)
   > 
   >     for i in range(loops):
-  >         ui.progress(topiclabel, i, 'loop.%d' % i, 'loopnum', total)
+  >         ui.progress(topiclabel, i, getloopitem(i), 'loopnum', total)
   >         if opts.get('parallel'):
   >             ui.progress('other', i, 'other.%d' % i, 'othernum', total)
   >         if nested:
@@ -48,6 +48,8 b''
   >     ui.progress(topiclabel, None, 'loop.done', 'loopnum', total)
   > 
   > topiclabel = 'loop'
+  > def getloopitem(i):
+  >     return 'loop.%d' % i
   > 
   > EOF
 
@@ -293,3 +295,42 b' are different from each other.'
   \xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88 [==>      ]\r (no-eol) (esc)
   \xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88 [=====>   ]\r (no-eol) (esc)
                        \r (no-eol) (esc)
+
+test triming progress items, when they contain multi-byte characters,
+of which length of byte sequence and columns in display are different
+from each other.
+
+  $ rm -f loop.pyc
+  $ cat >> loop.py <<EOF
+  > # use non-ascii characters as loop items of progress
+  > loopitems = [
+  >     u'\u3042\u3044\u3046'.encode('utf-8'), # 2 x 3 = 6 columns
+  >     u'\u3042\u3044\u3046\u3048'.encode('utf-8'), # 2 x 4 = 8 columns
+  > ]
+  > def getloopitem(i):
+  >     return loopitems[i % len(loopitems)]
+  > EOF
+
+  $ cat >> $HGRCPATH <<EOF
+  > [progress]
+  > # trim at tail side
+  > format = item+6
+  > EOF
+
+  $ hg --encoding utf-8 -y loop --total 2 2
+  \r (no-eol) (esc)
+  \xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\r (no-eol) (esc)
+  \xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\r (no-eol) (esc)
+                       \r (no-eol) (esc)
+
+  $ cat >> $HGRCPATH <<EOF
+  > [progress]
+  > # trim at left side
+  > format = item-6
+  > EOF
+
+  $ hg --encoding utf-8 -y loop --total 2 2
+  \r (no-eol) (esc)
+  \xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\r (no-eol) (esc)
+  \xe3\x81\x84\xe3\x81\x86\xe3\x81\x88\r (no-eol) (esc)
+                       \r (no-eol) (esc)