git.py: properly handle single-character flags with arguments

"git diff -U5" is correct while "git diff -U 5" is not.
ditto for "git log -U5", "git commit -F/some/path", etc.

The original version of transform_kwargs was setting up the
command line arguments such that single-character flags with
arguments were not understood by git.

This changes transform_kwargs so that the flag and argument
are both part of the same string for single-character flags.

Signed-off-by: David Aguilar <davvid@gmail.com>

Author: davvid

lib/git_python/git.py

@@ -44,8 +44,7 @@ def transform_kwargs(self, **kwargs):
                 if v is True:
                     args.append("-%s" % k)
                 else:
-                    args.append("-%s" % k)
-                    args.append(v)
+                    args.append("-%s%s" % (k, v))
             else:
                 if v is True:
                     args.append("--%s" % dashify(k))