templater: show the style list when I try to use a wrong one

When someone try to use a wrong style, a list with sugestions will appear.

In the test-log.t file it's a test that prove this thing.

mercurial/templater.py

@@ -394,6 +394,16 b' class engine(object):'
 
 engines = {'default': engine}
 
+def stylelist():
+    path = templatepath()[0]
+    dirlist =  os.listdir(path)
+    stylelist = []
+    for file in dirlist:
+        split = file.split(".")
+        if split[0] == "map-cmdline":
+            stylelist.append(split[1])
+    return ", ".join(stylelist)
+
 class templater(object):
 
     def __init__(self, mapfile, filters={}, defaults={}, cache={},
@@ -415,7 +425,8 b' class templater(object):'
         if not mapfile:
             return
         if not os.path.exists(mapfile):
-            raise util.Abort(_('style not found: %s') % mapfile)
+            raise util.Abort(_("style '%s' not found") % mapfile,
+                             hint=_("available styles: %s") % stylelist())
 
         conf = config.config()
         conf.read(mapfile)

tests/test-log.t

@@ -84,6 +84,14 b' log on directory'
   abort: cannot follow file not in parent revision: "dir"
   [255]
 
+-f, a wrong style
+
+  $ hg log -f -l1 --style something
+  abort: style 'something' not found
+  (available styles: changelog, bisect, default, xml, compact)
+  [255]
+
+
 -f, but no args
 
   $ hg log -f