docs: update README

README.md

@@ -1,44 +1,59 @@
 # MODFLOW 6 nightly build
 
-Bleeding-edge development build of MODFLOW 6 binaries.
+Nightly development build of MODFLOW 6.
 
 [![Latest tag](https://img.shields.io/github/tag/MODFLOW-USGS/modflow6-nightly-build.svg)](https://github.com/MODFLOW-USGS/modflow6-nightly-build/tags/latest)
 [![MODFLOW 6 intel nightly build](https://github.com/MODFLOW-USGS/modflow6-nightly-build/actions/workflows/nightly-build-intel.yml/badge.svg)](https://github.com/MODFLOW-USGS/modflow6-nightly-build/actions/workflows/nightly-build-intel.yml)
 [![MODFLOW 6 full distribution test](https://github.com/MODFLOW-USGS/modflow6-nightly-build/actions/workflows/full-dist-test.yml/badge.svg)](https://github.com/MODFLOW-USGS/modflow6-nightly-build/actions/workflows/full-dist-test.yml)
 
-The `develop` branch of the [MODFLOW 6 repository](https://github.com/MODFLOW-USGS/modflow6) contains bug fixes and new functionality that may be incorporated into the next [approved MODFLOW 6 release](https://www.usgs.gov/software/modflow-6-usgs-modular-hydrologic-model). Each night, as well as whenever code is merged into the `develop` branch, a workflow runs here to compile MODFLOW 6 with Intel Fortran on `windows-2022`, `macos-12`, and `ubuntu-22.04` runner images. The binaries are then posted as a [release on this repository](https://github.com/MODFLOW-USGS/modflow6-nightly-build/releases/latest). Binaries posted here are release candidates for the next approved version of MODFLOW 6 but are considered preliminary or provisional.
-
-**Note**: though this repository is named "nightly", a development distribution is created whenever code is merged into the `develop` branch of the MODFLOW 6 repository. If a release has already been created for the current date, assets are updated on the existing release.
+The `develop` branch of the [MODFLOW 6 repository](https://github.com/MODFLOW-USGS/modflow6) contains bug fixes and new functionality that may be incorporated into the next [approved MODFLOW 6 release](https://www.usgs.gov/software/modflow-6-usgs-modular-hydrologic-model). Each night, MODFLOW 6 is compiled with Intel Fortran on `windows-2022`, `macos-12`, and `ubuntu-20.04` runner images. A minimal development distribution is posted as a [release on this repository](https://github.com/MODFLOW-USGS/modflow6-nightly-build/releases/latest). Binaries should be considered preliminary or provisional release candidates for the next version of MODFLOW 6.
 
 <!-- START doctoc generated TOC please keep comment here to allow auto update -->
 <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
 
+
 - [Distribution contents](#distribution-contents)
-- [Linux compatibility](#linux-compatibility)
+ - [Binaries](#binaries)
+ - [Documentation](#documentation)
+ - [Tags](#tags)
 - [Reporting issues](#reporting-issues)
 - [Disclaimer](#disclaimer)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 
 ## Distribution contents
 
-The nightly builds are available as operating-system specific [release assets](https://github.com/MODFLOW-USGS/modflow6-nightly-build/releases/latest) (`win64.zip`, `mac.zip`, and `linux.zip`). The distribution includes: 
+The nightly builds are available as operating-system specific [distributions](https://github.com/MODFLOW-USGS/modflow6-nightly-build/releases/latest) (`mf6.y.zdev_win64.zip`, `..._mac.zip`, `..._linux.zip`). Each includes two directories, `bin` and `doc`, and a `code.json` metadata file. 
 
-1. **mf6[.exe]**: MODFLOW 6
-2. **mf5to6[.exe]**: the MODFLOW 5 to 6 converter
-3. **zbud6[.exe]**: the zone budget utility for MODFLOW 6
-4. **libmf6[.dll/so/dylib]**: a dynamic-linked library or shared object version of MODFLOW 6
-5. **code.json**: a JSON file containing version information and other metadata
+**mf6.y.zdev_...**
 
-Each release also includes a copy of the *'MODFLOW 6 – Description of Input and Output'* document (`mf6io.pdf`) for the [latest MODFLOW 6 release candidate](https://github.com/MODFLOW-USGS/modflow6-nightly-build/releases/latest).
+- **code.json**: a JSON file with version information and other metadata
 
-Release tags are based on the date, with format `YYYYMMDD`. Nightly builds are retained for 30 days in the event that there are issues with the latest release candidate. 
+- **bin/**
+
+ 1. **mf6[.exe]**: MODFLOW 6
+ 2. **mf5to6[.exe]**: the MODFLOW 5 to 6 converter
+ 3. **zbud6[.exe]**: the zone budget utility for MODFLOW 6
+ 4. **libmf6[.dll/so/dylib]**: a dynamic-linked library or shared object version of MODFLOW 6
+
+- **doc/**
 
+ 1. **release.pdf**: release notes
+ 2. **mf6io.pdf**: input/output documentation
 
-## Linux compatibility
+### Binaries
 
-The Linux binaries are built on Ubuntu 22.04 and may encounter `libc`-related backwards-incompatibilities on earlier versions of Ubuntu or other Linux distributions. The [`MODFLOW-USGS/executables`](https://github.com/MODFLOW-USGS/executables/releases) distribution is built on Ubuntu 20.04 and is known to be compatible with 18.04-22.04.
+The binaries are built in develop mode. The Windows distribution also contains `.pdb` files.
 
+Linux binaries built on Ubuntu 22.04 may encounter `libc`-related backwards-incompatibilities on earlier versions of Ubuntu or other Linux distributions. This distribution, the main MODFLOW 6 distribution, and the [`MODFLOW-USGS/executables`](https://github.com/MODFLOW-USGS/executables/releases) distribution are built on Ubuntu 20.04 for broader compatibility.
+
+### Documentation
+
+Each release also includes a copy of the *'MODFLOW 6 – Description of Input and Output'* document (`mf6io.pdf`) for the [latest MODFLOW 6 release candidate](https://github.com/MODFLOW-USGS/modflow6-nightly-build/releases/latest).
+
+### Tags
+
+Release tags are based on the date, with format `YYYYMMDD`. Nightly builds are retained for 30 days in the event that there are issues with the latest release candidate. 
 
 ## Reporting issues