Enable tilde and environment variable expansion on some items

Expand environment variables in the following configuration items:
- general.pythonfile;
- general.metadata;
- mbnames.filename;
- Repository.localfolders.
- Repository.sslcacertfile.

Make tilde and environment variable expansion in the following
configuration items:
- Repository.sslclientcert;
- Repository.sslclientkey.

GitHub pull request: https://github.com/OfflineIMAP/offlineimap/pull/113
Signed-off-by: Eygene Ryabinkin <rea@codelabs.ru>

offlineimap/CustomConfig.py

@@ -94,7 +94,7 @@ class CustomConfigParser(SafeConfigParser):
             return default
 
     def getmetadatadir(self):
-        xforms = [os.path.expanduser]
+        xforms = [os.path.expanduser, os.path.expandvars]
         d = self.getdefault("general", "metadata", "~/.offlineimap")
         metadatadir = self.apply_xforms(d, xforms)
         if not os.path.exists(metadatadir):
@@ -102,7 +102,7 @@ class CustomConfigParser(SafeConfigParser):
         return metadatadir
 
     def getlocaleval(self):
-        xforms = [os.path.expanduser]
+        xforms = [os.path.expanduser, os.path.expandvars]
         if self.has_option("general", "pythonfile"):
             path = self.apply_xforms(self.get("general", "pythonfile"), xforms)
         else:

offlineimap/mbnames.py

@@ -49,12 +49,14 @@ def write():
 def __genmbnames():
     """Takes a configparser object and a boxlist, which is a list of hashes
     containing 'accountname' and 'foldername' keys."""
+    xforms = [os.path.expanduser, os.path.expandvars]
     mblock.acquire()
     try:
         localeval = config.getlocaleval()
         if not config.getdefaultboolean("mbnames", "enabled", 0):
             return
-        file = open(os.path.expanduser(config.get("mbnames", "filename")), "wt")
+        path = config.apply_xform(config.get("mbnames", "filename"), xforms)
+        file = open(path, "wt")
         file.write(localeval.eval(config.get("mbnames", "header")))
         folderfilter = lambda accountname, foldername: 1
         if config.has_option("mbnames", "folderfilter"):

offlineimap/repository/IMAP.py

@@ -194,14 +194,16 @@ class IMAPRepository(BaseRepository):
         return self.getconfboolean('ssl', 0)
 
     def getsslclientcert(self):
-        return self.getconf('sslclientcert', None)
+        xforms = [os.path.expanduser, os.path.expandvars, os.path.abspath]
+        return self.getconf_xform('sslclientcert', xforms, None)
 
     def getsslclientkey(self):
-        return self.getconf('sslclientkey', None)
+        xforms = [os.path.expanduser, os.path.expandvars, os.path.abspath]
+        return self.getconf_xform('sslclientkey', xforms, None)
 
     def getsslcacertfile(self):
         """Return the absolute path of the CA certfile to use, if any"""
-        xforms = [os.path.expanduser, os.path.abspath]
+        xforms = [os.path.expanduser, os.path.expandvars, os.path.abspath]
         cacertfile = self.getconf_xform('sslcacertfile', xforms,
           get_os_sslcertfile())
         if cacertfile is None: