doc: reorganize and extend documentation

doc/BUILD.bazel

@@ -1 +0,0 @@
-exports_files(["PathPolicy.md"])

doc/beacon-metadata.rst

@@ -236,7 +236,7 @@ For now it distinguishes three different types of links:
 Use cases of such information include:
 
 -  Mitigating security concerns.
--  Allowing users to select paths that e.g. avoid the open internet.
+-  Allowing users to select paths that e.g. avoid the open Internet.
 
 Internal Hops
 -------------

doc/conf.py

@@ -1,20 +1,9 @@
 # Configuration file for the Sphinx documentation builder.
 #
-# This file only contains a selection of the most common options. For a full
-# list see the documentation:
+# See documentation:
 # https://www.sphinx-doc.org/en/master/usage/configuration.html
 
-# -- Path setup --------------------------------------------------------------
-
-# 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
-# documentation root, use os.path.abspath to make it absolute, like shown here.
-#
-# import os
-# import sys
-# sys.path.insert(0, os.path.abspath('.'))
-
-import sphinx_rtd_theme  # noqa
+import subprocess
 
 # -- Project information -----------------------------------------------------
 
@@ -31,6 +20,7 @@
 extensions = [
     'recommonmark',
     'sphinx_rtd_theme',
+    'sphinx.ext.extlinks',
 ]
 
 # Add any paths that contain templates here, relative to this directory.
@@ -43,18 +33,53 @@
     'venv', 'requirements.in', 'requirements.txt',
     '_build', 'Thumbs.db', '.DS_Store',
     'manuals/*/*',  # manuals/<x>.rst uses "include" directive to compose files from subdirectories
+    'dev/design/TEMPLATE.rst',
 ]
 
 master_doc = 'index'
 
+nitpicky = True
+
+option_emphasise_placeholders = True
+
+# -- extlinks definitions for links to github ---
+
+# Determine current git commit for permalinks to files on github.
+# Note: somewhat obviously, these links will only work if the current rev has been pushed.
+try:
+    file_ref_commit = subprocess.run(
+        ['git', 'rev-parse', "HEAD"],
+        capture_output=True, text=True, check=True
+    ).stdout.strip()
+except subprocess.CalledProcessError:
+    file_ref_commit = "master"  # only used on unexpected problem with executing git
+
+extlinks = {
+    # :issue:`123` is an issue link displayed as "#123"
+    'issue': ('https://github.com/scionproto/scion/issues/%s', '#%s'),
+    # :file-ref:`foo/bar.go` is a link to a file in the repo, displayed as "foo/bar.go"
+    'file-ref': ('https://github.com/scionproto/scion/blob/'+file_ref_commit+'/%s', '%s'),
+}
+
 # -- Options for HTML output -------------------------------------------------
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
 #
 html_theme = 'sphinx_rtd_theme'
 
+html_theme_options = dict(
+    style_external_links=True,
+)
+
+manpages_url = "https://manpages.debian.org/{path}"
+
+
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
 html_static_path = ['']
+
+html_css_files = [
+    'css/custom.css',
+]