add first draft of reproducible build documentation

README.md

@@ -23,7 +23,7 @@ When updating to the latest HEAD
 
 `git pull --recurse-submodules`
 
-The release binaries are reproducible (pre codesigning and installer packaging at this time).
+The release binaries are reproducible from v1.5.0 onwards (pre codesigning and installer packaging). More detailed [instructions on reproducing the binaries](docs/reproducible.md) are provided.
 
 ## Running
 

docs/README.md

@@ -0,0 +1,11 @@
+## Sparrow Wallet Repository Docs
+
+Note that most documentation for the project can be found at https://sparrowwallet.com/docs/. 
+The documentation here is mainly developer-related resources.
+
+### [Reproducible builds](reproducible.md)
+
+Documentation to create and verify a build of the project against the released binaries.
+
+
+

docs/reproducible.md

@@ -0,0 +1,78 @@
+## Reproducible builds
+
+Reproducibility is a goal of the Sparrow Wallet project. 
+As of v1.5.0 and later, it is possible to recreate the exact binaries in the Github releases (specifically, the contents of the `.tar.gz` and `.zip` files).
+
+Due to minor variances, it is not yet possible to reproduce the installer packages (`.deb`, `.rpm` and `.exe`).
+In addition, the OSX binary is code signed and thus can't be directly reproduced yet. 
+Work on resolving both of these issues is ongoing.
+
+### Reproducing a release
+
+#### Install Java
+
+Because Sparrow bundles a Java runtime in the release binaries, it is essential to have the same version of Java installed when creating the release.
+For v1.5.0 and later, this is AdoptOpenJdk jdk-16.0.1+9 Hotspot. 
+It is available for all supported platforms from the [AdoptOpenJdk site](https://adoptopenjdk.net/archive.html?variant=openjdk16&jvmVariant=hotspot).
+
+For reference, the downloads are as follows:
+- [Linux x64](https://github.com/AdoptOpenJDK/openjdk16-binaries/releases/download/jdk-16.0.1%2B9/OpenJDK16U-jdk_x64_linux_hotspot_16.0.1_9.tar.gz)
+- [MacOS x64](https://github.com/AdoptOpenJDK/openjdk16-binaries/releases/download/jdk-16.0.1%2B9/OpenJDK16U-jdk_x64_mac_hotspot_16.0.1_9.tar.gz)
+- [Windows x64](https://github.com/AdoptOpenJDK/openjdk16-binaries/releases/download/jdk-16.0.1%2B9/OpenJDK16U-jdk_x64_windows_hotspot_16.0.1_9.zip)
+
+It is also possible to install via a package manager on *nix systems. For example, on Debian/Ubuntu systems:
+```shell
+sudo apt-get install -y wget apt-transport-https gnupg
+wget https://adoptopenjdk.jfrog.io/adoptopenjdk/api/gpg/key/public
+gpg --no-default-keyring --keyring ./adoptopenjdk-keyring.gpg --import public
+gpg --no-default-keyring --keyring ./adoptopenjdk-keyring.gpg --export --output adoptopenjdk-archive-keyring.gpg
+rm adoptopenjdk-keyring.gpg
+sudo mv adoptopenjdk-archive-keyring.gpg /usr/share/keyrings
+sudo apt update -y
+sudo apt-get install -y adoptopenjdk-16-hotspot=16.0.1+9-3
+```
+
+A alternative option for all platforms is to use the [sdkman.io](sdkman.io) package manager ([Git Bash for Windows](https://git-scm.com/download/win) is a good choice on that platform).
+See the installation [instructions here](https://sdkman.io/install).
+Once installed, run
+```shell
+sdk install java 16.0.1.hs-adpt
+```
+
+#### Other requirements
+
+Other packages may also be necessary to build depending on the platform. On Debian/Ubuntu systems:
+```shell
+sudo apt install -y rpm
+```
+
+#### Building the binaries
+
+The project can cloned for a specific release tag as follows:
+```shell
+GIT_TAG="1.5.0-beta1"
+git clone --recursive git@github.com:sparrowwallet/sparrow.git
+git checkout --quiet "${GIT_TAG}"
+```
+
+Thereafter, building should be straightforward:
+
+```shell
+cd sparrow
+./gradlew jpackage
+```
+
+The binaries (and installers) will be placed in the `build/jpackage` folder.
+
+#### Verifying the binaries are identical
+
+Note that you will be verifying the files in the `build/jpackage/Sparrow` folder against either the `.tar.gz` or `.zip` releases.
+Download either of these depending on your platform and extract the contents to a folder (in the following example, `/tmp`).
+Then compare all of the folders and files recursively:
+
+```shell
+diff -r build/jpackage/Sparrow /tmp/Sparrow
+```
+
+This command should have no output indicating that the two folders (and all their contents) are identical.
+