patman: Handle creation of patman config file

patman shouts when it couldn't find a $(HOME)/.patman file.
Handle it in a sane way by creating a new one for the user.
It looks for a user.name and user.email in the global .gitconfig
file, waits for the user input if it can't find there. Update the
same in the README

Signed-off-by: Vikram Narayanan <vikram186@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
Cc: Simon Glass <sjg@chromium.org>
Cc: Wolfgang Denk <wd@denx.de>

tools/patman/gitutil.py

@@ -357,6 +357,24 @@ def GetAliasFile():
         fname = os.path.join(GetTopLevel(), fname.strip())
     return fname
 
+def GetDefaultUserName():
+    """Gets the user.name from .gitconfig file.
+
+    Returns:
+        User name found in .gitconfig file, or None if none
+    """
+    uname = command.OutputOneLine('git', 'config', '--global', 'user.name')
+    return uname
+
+def GetDefaultUserEmail():
+    """Gets the user.email from the global .gitconfig file.
+
+    Returns:
+        User's email found in .gitconfig file, or None if none
+    """
+    uemail = command.OutputOneLine('git', 'config', '--global', 'user.email')
+    return uemail
+
 def Setup():
     """Set up git utils, by reading the alias files."""
     settings.Setup('')