Factor out common code

src/cdiff.py

     'lightcyan'     : '\x1b[1;36m',
 }
 
+
+# Keys for checking and values for diffing.
+REVISION_CONTROL = (
+    (['git', 'rev-parse'], ['git', 'diff']),
+    (['svn', 'info'], ['svn', 'diff']),
+    (['hg', 'summary'], ['hg', 'diff'])
+)
+
+
 def ansi_code(color):
     return COLORS.get(color, '')
 
         return False
 
 
+def command_pipe(arguments):
+    """Return stdout pipe after starting subprocess."""
+    return subprocess.Popen(arguments, stdout=subprocess.PIPE).stdout
+
+
 def revision_control_diff(path):
     """Return diff from revision control system."""
-    if check_command_status(['git', 'rev-parse']):
-        return subprocess.Popen(['git', 'diff'], stdout=subprocess.PIPE).stdout
-    elif check_command_status(['svn', 'info']):
-        return subprocess.Popen(['svn', 'diff'], stdout=subprocess.PIPE).stdout
-    elif check_command_status(['hg', 'summary']):
-        return subprocess.Popen(['hg', 'diff'], stdout=subprocess.PIPE).stdout
+    for check, diff in REVISION_CONTROL:
+        if check_command_status(check):
+            return command_pipe(diff)
 
 
 def decode(line):