Add common alias distcalc (j)

pygmt/helpers/decorators.py

@@ -39,6 +39,20 @@
     "W": """\
         pen : str
             Set pen attributes for lines or the outline of symbols.""",
+    "j": """\
+        distcalc : str
+            ``e|f|g``.
+            Determine how spherical distances are calculated.
+
+            - **e** - Ellipsoidal (or geodesic) mode
+            - **f** - Flat Earth mode
+            - **g** - Great circle distance [Default]
+
+            All spherical distance calculations depend on the current ellipsoid
+            (PROJ_ELLIPSOID), the definition of the mean radius
+            (PROJ_MEAN_RADIUS), and the specification of latitude type
+            (PROJ_AUX_LATITUDE). Geodesic distance calculations is also
+            controlled by method (PROJ_GEODESIC).""",
     "n": """\
         interpolation : str
             ``[b|c|l|n][+a][+bBC][+c][+tthreshold]``