API fix for apt.list_pkgs

apt.patch

jeff@desktopmonster:~/src/git/salt/salt/modules (misc-fixes)$ gdi apt.py
diff --git a/salt/modules/apt.py b/salt/modules/apt.py
index f3b0cd8..75751a4 100644
--- a/salt/modules/apt.py
+++ b/salt/modules/apt.py
@@ -196,7 +196,7 @@ def upgrade(refresh=True):
     return ret_pkgs
 
 
-def list_pkgs(regex_string=""):
+def list_pkgs(package_name="", regex_string=""):
     '''
     List the packages currently installed in a dict:
     {'<package_name>': '<version>'}
@@ -205,12 +205,16 @@ def list_pkgs(regex_string=""):
     salt '*' pkg.list_pkgs
     '''
     ret = {}
-    cmd = 'dpkg --list ' + regex_string
+    cmd = 'dpkg --list ' + package_name
     
     out = subprocess.Popen(cmd,
             shell=True,
             stdout=subprocess.PIPE).communicate()[0].split('\n')
     
+    if regex_string:
+        regex = re.compile(regex_string)
+        out = filter(regex.match, out)
+
     for line in out:
         cols = line.split()
         if len(cols) and cols[0].count('ii'):