Ensure spaces in pygmt.config arguments can work

Also added a regression test for
FORMAT_DATE_MAP="o dd".

pygmt/src/config.py

@@ -55,7 +55,7 @@ def __init__(self, **kwargs):
  self.old_defaults[key] = lib.get_default(key)
 
  # call gmt set to change GMT defaults
- arg_str = " ".join([f"{key}={value}" for key, value in kwargs.items()])
+ arg_str = " ".join([f'{key}="{value}"' for key, value in kwargs.items()])
  with Session() as lib:
  lib.call_module("set", arg_str)
 

pygmt/tests/baseline/test_config_format_date_map.png.dvc

@@ -0,0 +1,4 @@
+outs:
+- md5: 3619720cdfcd857cbdbb49ed7fe6e930
+ size: 1392
+ path: test_config_format_date_map.png

pygmt/tests/test_config.py

@@ -64,6 +64,25 @@ def test_config_font_annot():
  return fig
 
 
+@pytest.mark.mpl_image_compare
+def test_config_format_date_map():
+ """
+ Test that setting FORMAT_DATE_MAP config changes how the output date string
+ is plotted.
+
+ Note the space in 'o dd', this acts as a regression test for
+ https://github.com/GenericMappingTools/pygmt/issues/247.
+ """
+ fig = Figure()
+ with config(FORMAT_DATE_MAP="o dd"):
+ fig.basemap(
+ region=["1969-7-21T", "1969-7-23T", 0, 1],
+ projection="X2.5c/0.1c",
+ frame=["sxa1D", "S"],
+ )
+ return fig
+
+
 @pytest.mark.mpl_image_compare
 def test_config_format_time_map():
  """