color: enabled color support for export command (issue1507)

color: enabled color support for export command (issue1507)

The export command didn't output the diffs in color, even when color support
was enabled. This patch fixes that by making the export command use the default
ui.write method, instead of directly manipulating the ui.fout file object.
Also added a test case to verify color output to test-export.t.

--- a/mercurial/cmdutil.py	Thu Sep 06 22:51:32 2012 +0200
+++ b/mercurial/cmdutil.py	Mon Aug 27 09:37:49 2012 -0700
@@ -547,30 +547,37 @@
         prev = (parents and parents[0]) or nullid
 
         shouldclose = False
-        if not fp:
+        if not fp and len(template) > 0:
             desc_lines = ctx.description().rstrip().split('\n')
             desc = desc_lines[0]    #Commit always has a first line.
             fp = makefileobj(repo, template, node, desc=desc, total=total,
                              seqno=seqno, revwidth=revwidth, mode='ab')
             if fp != template:
                 shouldclose = True
-        if fp != sys.stdout and util.safehasattr(fp, 'name'):
+        if fp and fp != sys.stdout and util.safehasattr(fp, 'name'):
             repo.ui.note("%s\n" % fp.name)
 
-        fp.write("# HG changeset patch\n")
-        fp.write("# User %s\n" % ctx.user())
-        fp.write("# Date %d %d\n" % ctx.date())
+        if not fp:
+            write = repo.ui.write
+        else:
+            def write(s, **kw):
+                fp.write(s)
+
+
+        write("# HG changeset patch\n")
+        write("# User %s\n" % ctx.user())
+        write("# Date %d %d\n" % ctx.date())
         if branch and branch != 'default':
-            fp.write("# Branch %s\n" % branch)
-        fp.write("# Node ID %s\n" % hex(node))
-        fp.write("# Parent  %s\n" % hex(prev))
+            write("# Branch %s\n" % branch)
+        write("# Node ID %s\n" % hex(node))
+        write("# Parent  %s\n" % hex(prev))
         if len(parents) > 1:
-            fp.write("# Parent  %s\n" % hex(parents[1]))
-        fp.write(ctx.description().rstrip())
-        fp.write("\n\n")
+            write("# Parent  %s\n" % hex(parents[1]))
+        write(ctx.description().rstrip())
+        write("\n\n")
 
-        for chunk in patch.diff(repo, prev, node, opts=opts):
-            fp.write(chunk)
+        for chunk, label in patch.diffui(repo, prev, node, opts=opts):
+            write(chunk, label=label)
 
         if shouldclose:
             fp.close()

--- a/tests/test-export.t	Thu Sep 06 22:51:32 2012 +0200
+++ b/tests/test-export.t	Mon Aug 27 09:37:49 2012 -0700
@@ -144,4 +144,28 @@
   abort: export requires at least one changeset
   [255]
 
+Check for color output
+  $ echo "[color]" >> $HGRCPATH
+  $ echo "mode = ansi" >> $HGRCPATH
+  $ echo "[extensions]" >> $HGRCPATH
+  $ echo "color=" >> $HGRCPATH
+
+  $ hg export --color always --nodates tip
+  # HG changeset patch
+  # User test
+  # Date 0 0
+  # Node ID * (glob)
+  # Parent * (glob)
+   !"#$%&(,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
+  
+  \x1b[0;1mdiff -r f3acbafac161 -r 197ecd81a57f foo\x1b[0m (esc)
+  \x1b[0;31;1m--- a/foo\x1b[0m (esc)
+  \x1b[0;32;1m+++ b/foo\x1b[0m (esc)
+  \x1b[0;35m@@ -10,3 +10,4 @@\x1b[0m (esc)
+   foo-9
+   foo-10
+   foo-11
+  \x1b[0;32m+line\x1b[0m (esc)
+
+
   $ cd ..