refactor get_short_path into two functions

use this to replace the home directory in the new plain mode

segments/cwd.py

@@ -1,30 +1,38 @@
 import os
 
-def get_short_path(cwd):
+
+def replace_home_dir(cwd):
     home = os.getenv('HOME')
+    if cwd.startswith(home):
+        return '~' + cwd[len(home):]
+    return cwd
+
+
+def split_path_into_names(cwd):
     names = cwd.split(os.sep)
-    if names[0] == '': names = names[1:]
-    path = ''
-    for i in range(len(names)):
-        path += os.sep + names[i]
-        if os.path.samefile(path, home):
-            return ['~'] + names[i+1:]
+
+    if names[0] == '':
+        names = names[1:]
+
     if not names[0]:
         return ['/']
+
     return names
 
+
 def add_cwd_segment():
-    cwd = powerline.cwd or os.getenv('PWD')
-    names = get_short_path(cwd.decode('utf-8'))
+    cwd = (powerline.cwd or os.getenv('PWD')).decode('utf-8')
+    cwd = replace_home_dir(cwd)
+    names = split_path_into_names(cwd)
 
     max_depth = powerline.args.cwd_max_depth
     if len(names) > max_depth:
         names = names[:2] + [u'\u2026'] + names[2 - max_depth:]
 
-    if powerline.args.cwd_mode=='plain':
-        powerline.append(cwd, Color.CWD_FG, Color.PATH_BG)
+    if powerline.args.cwd_mode == 'plain':
+        powerline.append(' %s ' % (cwd,), Color.CWD_FG, Color.PATH_BG)
     else:
-        if not (powerline.args.cwd_mode=='dironly' or powerline.args.cwd_only):
+        if not (powerline.args.cwd_mode == 'dironly' or powerline.args.cwd_only):
             for n in names[:-1]:
                 if n == '~' and Color.HOME_SPECIAL_DISPLAY:
                     powerline.append(' %s ' % n, Color.HOME_FG, Color.HOME_BG)