Update release_docs HISTORY scheme (#2443)

We will no longer maintain HISTORY files for other maintenance branches,
so those have been removed. Adds a README.md explaining the purpose
and procedures of HDF5 HISTORY. Also adds a newsletter template and
updates the RELEASE.txt note part of CONTRIBUTING.md.

Also cleans out RELEASE.txt post-HDF5-1.14.0

1 files changed, 102 insertions, 0 deletions

diff --git a/release_docs/README.md b/release_docs/README.md
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+# The `release_docs` directory
+
+## Intro
+
+This directory contains instructions for building and using the library as
+well as the HDF5 history files.
+
+## HISTORY files
+
+The `HISTORY` files contain the history of this branch of HDF5. They fall into
+three categories.
+
+### HISTORY-\[VERSION 1\]-\[VERSION 2\].txt
+
+These files are created when we release a new major version and include all
+the changes that were made to the `develop` branch while creating a major release.
+
+### HISTORY-\[VERSION\].txt
+
+This file contains the changes that were made to a maintenance branch since
+it split off from `develop`. It will also be found in the `develop` branch
+when experimental releases have been created.
+
+### RELEASE.txt
+
+This is the changelog for the current version of the library.
+
+For a MAJOR release (or in `develop`) this files lists all the changes since the
+last major version. For a MINOR release (or in a maintenance branch), this file
+lists all the changes since the last release in the maintenance branch.
+
+Examples:
+
+* The file for HDF5 1.14.0 includes all the changes since HDF5 1.12.0
+* The file for HDF5 1.10.9 includes all the changes since HDF5 1.10.8
+* The file in `develop` includes all the changes since the last major release
+* The file in `hdf5_1_14` includes all the changes since the last minor HDF5 1.14 release
+
+Note that we make no effort to bring maintenance branch `HISTORY` files back to
+develop. If you want to compare, say, 1.10.4 with 1.12.3, you'd have to get
+the history files from those releases and compare them by hand.
+
+## Creating new releases
+
+### MAJOR release
+
+* If there were experimental releases, merge the experimental `HISTORY` file
+  and the current `RELEASE.txt` by category to create a separate, unified
+  file that ignores the experimental releases. Don't check this in yet or
+  clobber any existing `HISTORY`/`RELEASE` files, but put it someplace handy for
+  use in later steps.
+
+* Create the new maintenance branch
+
+In develop:
+* Create the new `HISTORY-\[VERSION 1\]-\[VERSION 2\].txt` file
+    * If there is an experimental `HISTORY` file, add `RELEASE.txt` to the beginning of it and use that
+    * Otherwise, start with `RELEASE.txt`
+    * Add the introduction boilerplate like in the other `HISTORY` files (TOC, etc.)
+* Delete any experimental `HISTORY` file
+* Clear out `RELEASE.txt`
+
+Note that we're KEEPING any experimental release history information in the
+`HISTORY-\[VERSION 1\]-\[VERSION 2\].txt` file, so do NOT use the merged file in
+the above steps!
+
+In the new maintenance branch:
+* Create the new `HISTORY-\[VERSION\].txt` file
+    * If there is an experimental `HISTORY` file use the combined file you created earlier
+    * Otherwise, start with `RELEASE.txt`
+    * Add the introduction boilerplate like in the other `HISTORY` files (TOC, etc.)
+* Delete any experimental `HISTORY` file
+* Clear out `RELEASE.txt`
+
+* Create the new release branch
+
+In the new release branch:
+* If there were experimental releases, use the combined file you created earlier as `RELEASE.txt`
+* Otherwise the `RELEASE.txt` will be used as-is
+
+### MINOR release
+
+* Create the release branch
+
+In the maintenance branch:
+* Add the contents of `RELEASE.txt` to the beginnnig of `HISTORY-\[VERSION\].txt`
+* Clear out `RELEASE.txt`
+
+### EXPERIMENTAL release
+
+* Add the contents of `RELEASE.txt` to the beginnnig of `HISTORY-\[VERSION\].txt`
+* Clear out `RELEASE.txt`
+
+## INSTALL files
+
+These files include instructions for building and installing HDF5 on various
+platforms.
+
+## USING files
+
+These files document how to build HDF5 applications with an installed HDF5
+library.