progress: use 'encoding.colwidth' to get column width of output line correctly

Before this patch, 'progress' extension applies 'len' on byte sequence
to get column width of it, but it causes incorrect result, when length
of byte sequence and columns in display are different from each other
in multi-byte characters.

This patch uses 'encoding.colwidth' to get column width of output line
correctly, even if it contains multi-byte characters.

hgext/progress.py

@@ -159,9 +159,9 class progbar(object):
         if needprogress:
             used = 0
             if head:
-                used += len(head) + 1
+                used += encoding.colwidth(head) + 1
             if tail:
-                used += len(tail) + 1
+                used += encoding.colwidth(tail) + 1
             progwidth = termwidth - used - 3
             if total and pos <= total:
                 amt = pos * progwidth // total

tests/test-progress.t

@@ -275,3 +275,21 display are different from each other.
   \xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88 1/3\r (no-eol) (esc)
   \xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88 2/3\r (no-eol) (esc)
               \r (no-eol) (esc)
+
+test calculation of bar width, when progress topic contains multi-byte
+characters, of which length of byte sequence and columns in display
+are different from each other.
+
+  $ cat >> $HGRCPATH <<EOF
+  > [progress]
+  > format = topic bar
+  > width= 21
+  > # progwidth should be 9 (= 21 - (8+1) - 3)
+  > EOF
+
+  $ hg --encoding utf-8 -y loop --total 3 3
+  \r (no-eol) (esc)
+  \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)
+  \xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88 [=====>   ]\r (no-eol) (esc)
+                       \r (no-eol) (esc)