Merge pull request gitpython-developers#43 from swallat/master

Fixed 'Inappropriate ioctl for device' problem on posix systems

Without an active login shell on linux or osx, we now use the password database to obtain the active login, instead of relying on environment variables).

Author: Byron

git/util.py

@@ -20,7 +20,9 @@
 					SlidingWindowMapManager,
 					SlidingWindowMapBuffer
 				)
-
+# Import the user database on unix based systems
+if os.name == "posix":
+    import pwd
 
 
 __all__ = ( "stream_copy", "join_path", "to_native_path_windows", "to_native_path_linux", 
@@ -144,12 +146,17 @@ def __getslice__(self, start, end):
 
 def get_user_id():
 	""":return: string identifying the currently active system user as name@node
-	:note: user can be set with the 'USER' environment variable, usually set on windows"""
-	ukn = 'UNKNOWN'
-	username = os.environ.get('USER', os.environ.get('USERNAME', ukn))
-	if username == ukn and hasattr(os, 'getlogin'):
-		username = os.getlogin()
-	# END get username from login
+	:note: user can be set with the 'USER' environment variable, usually set on windows
+	:note: on unix based systems you can use the password database
+	to get the login name of the effective process user"""
+        if os.name == "posix":
+                username = pwd.getpwuid(os.geteuid()).pw_name
+        else:
+	        ukn = 'UNKNOWN'
+	        username = os.environ.get('USER', os.environ.get('USERNAME', ukn))
+	        if username == ukn and hasattr(os, 'getlogin'):
+		        username = os.getlogin()
+	        # END get username from login
 	return "%s@%s" % (username, platform.node())
 
 def is_git_dir(d):