DOC: Link to code and version automation feature is implemented.

Link to code implementation depends on https://github.com/OceanParcels/parcels/blob/cac7ed05e8b250b3c6d5830d08e9d070e3217242/parcels/_version.py#L4

Docs version in conf.py now uses parcels.__version__

docs/conf.py

@@ -12,8 +12,10 @@
 # All configuration values have a default; values that are commented out
 # serve to show the default.
 
-import sys
+import inspect
 import os
+import sys
+import warnings
 
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
@@ -31,7 +33,7 @@
 extensions = [
     'sphinx.ext.autodoc',
     'sphinx.ext.todo',
-    'sphinx.ext.viewcode',
+    "sphinx.ext.linkcode",
 ]
 
 # Add any paths that contain templates here, relative to this directory.
@@ -58,9 +60,11 @@
 # built documents.
 #
 # The short X.Y version.
-version = '2.4.0'
+import parcels
+
+version = parcels.__version__
 # The full version, including alpha/beta/rc tags.
-release = '2.4.0'
+release = version
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
@@ -162,6 +166,65 @@
     "doc_path": "docs",
 }
 
+# based on pandas doc/source/conf.py
+def linkcode_resolve(domain, info):
+    """Determine the URL corresponding to Python object."""
+    if domain != "py":
+        return None
+
+    modname = info["module"]
+    fullname = info["fullname"]
+
+    submod = sys.modules.get(modname)
+    if submod is None:
+        return None
+
+    obj = submod
+    for part in fullname.split("."):
+        try:
+            with warnings.catch_warnings():
+                # Accessing deprecated objects will generate noisy warnings
+                warnings.simplefilter("ignore", FutureWarning)
+                obj = getattr(obj, part)
+        except AttributeError:
+            return None
+
+    try:
+        fn = inspect.getsourcefile(inspect.unwrap(obj))
+    except TypeError:
+        try:  # property
+            fn = inspect.getsourcefile(inspect.unwrap(obj.fget))
+        except (AttributeError, TypeError):
+            fn = None
+    if not fn:
+        return None
+
+    try:
+        source, lineno = inspect.getsourcelines(obj)
+    except TypeError:
+        try:  # property
+            source, lineno = inspect.getsourcelines(obj.fget)
+        except (AttributeError, TypeError):
+            lineno = None
+    except OSError:
+        lineno = None
+
+    if lineno:
+        linespec = f"#L{lineno}-L{lineno + len(source) - 1}"
+    else:
+        linespec = ""
+
+    fn = os.path.relpath(fn, start=os.path.dirname(parcels.__file__))
+
+    if "-" in parcels.__version__:
+        return f"https://github.com/OceanParcels/parcels/blob/master/parcels/{fn}{linespec}"
+    else:
+        return (
+            f"https://github.com/OceanParcels/parcels/blob/"
+            f"{parcels.__version__}/parcels/{fn}{linespec}"
+        )
+
+
 # Add any extra paths that contain custom files (such as robots.txt or
 # .htaccess) here, relative to this directory. These files are copied
 # directly to the root of the documentation.