docs/download.txt: revise notes on snapshots (not only GitHub now) and build types (git/dist) [#1400]

Signed-off-by: Jim Klimov <jimklimov+nut@gmail.com>

Author: jimklimov

docs/download.txt

@@ -11,9 +11,13 @@ This section presents the different methods to download NUT.
 Building from source code
 -------------------------
 
-You will need a number of tools such as `autoconf`, `automake` and `libtool`
-to use these checkouts or snapshots to generate the `configure` script and
-some other files.  A more complete list for different platforms can be seen in
+To build from Git sources, you will need a number of tools such as `autoconf`,
+`automake` and `libtool` to use these checkouts or snapshots to generate the
+`configure` script and some other files.  The distribution archives already
+include the `configure` script (as well as other files) and do not require
+auto* tools to prepare the sources for a build.
+
+A more complete list of build prerequisites for different platforms can be seen in
 link:https://networkupstools.org/docs/qa-guide.chunked/_prerequisites_for_building_nut_on_different_oses.html[Prerequisites
 for building NUT on different OSes] chapter in the
 link:https://networkupstools.org/docs/qa-guide.chunked/[NUT QA Guide],
@@ -134,21 +138,20 @@ sources of operating system distributions, as listed below.
 Snapshots
 ^^^^^^^^^
 
-GitHub has several download links for repository snapshots (for particular
-tags or branches), but note that the ability to build NUT seamlessly from
-ZIP or `tar.gz` snapshots prepared by GitHub automatically (as a `git archive`
-of a checked-out workspace) is not regularly checked nor "supported" by the
-Network UPS Tools project. YMMV.
-
-/////////
-TODO: #1400 to replace this with a NUT CI farm service to publish the tarballs
-
-If our Buildbot instance is behaving, you can download a snapshot which does
-not require auto* tools from this
-link:http://buildbot.networkupstools.org/snapshots[builder].  Look for the
-latest *[tarball]* link towards the top of the page, and be sure to check the
-'Build ##' link to verify the branch name.
-/////////
+For pull requests and eventual merges into the master branch, a NUT CI job
+prepares correct "dist tarballs" with a snapshot of source code, as well as
+an archive with rendered documentation files (PDF, HTML, man pages).
+
+Links to these "Dist and Docs" archives can be seen on GitHub in merge commit
+comments, and are posted as a rolling comment in pull requests. Keep in mind
+that artefacts like these are stored for up to 90 days, and can be rotated
+away earlier.
+
+NOTE: GitHub has several download links for repository snapshots (made for
+particular tags or branches), but the ability to build NUT seamlessly from
+ZIP or `tar.gz` snapshots prepared by GitHub automatically (as a simple
+`git archive` of a checked-out workspace) is not regularly checked nor
+"supported" by the Network UPS Tools project. YMMV.
 
 Older versions
 ~~~~~~~~~~~~~~