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PACKAGING.md

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Packager's Manual

Note: The guidance here applies to the current development version and release versions starting from 0.16.0. The details for earlier versions are different.

Elvish is a normal Go application, and doesn't require any special attention. Build the main package of cmd/elvish, and you should get a fully working binary.

If you don't care about accurate version information or reproducible builds, you can now stop reading. If you do, there is a small amount of extra work to get them.

Accurate version information

The pkg/buildinfo package contains a constant, Version, and a variable, VersionSuffix, which are concatenated to form the full version used in the output of elvish -version and elvish -buildinfo. Their values are set as follows:

  • At release tags, Version contains the version of the release, which is identical to the tag name. VersionSuffix is empty.

  • At development commits, Version contains the version of the next release. VersionSuffix is set to -dev.unknown.

The VersionSuffix variable can be overridden at build time, by passing -ldflags "-X github.com/markusbkk/elvish/pkg/buildinfo.VersionSuffix=-foobar" to go build, go install or go get. This is necessary in several scenarios, which are documented below.

Packaging release versions

If you are using the standard Go toolchain and not applying any patches, there is nothing more to do; the default empty VersionSuffix suffices.

If you are using a non-standard toolchain, or have applied any patches that can affect the resulting binary, you must override VersionSuffix with a string that starts with + and can uniquely identify your toolchain and patch. For official Linux distribution builds, this should identify your distribution, plus the version of the patch. Example:

go build -ldflags "-X github.com/markusbkk/elvish/pkg/buildinfo.VersionSuffix=+deb1" ./cmd/elvish

Packaging development builds

If you are packaging development builds, the default value of VersionSuffix, which is -dev.unknown, is likely not good enough, as it does not identify the commit Elvish is built from.

You should override VersionSuffix with -dev.$commit_hash, where $commit_hash is the full commit hash, which can be obtained with git rev-parse HEAD. Example:

go build -ldflags \
  "-X github.com/markusbkk/elvish/pkg/buildinfo.VersionSuffix=-dev.$(git rev-parse HEAD)" \
  ./cmd/elvish

If you have applied any patches that is not committed as a Git commit, you should also append a string that starts with + and can uniquely identify your patch.

Reproducible builds

The idea of reproducible build is that an Elvish binary from two different sources should be bit-to-bit identical, as long as they are built from the same version of the source code using the same version of the Go compiler.

To make reproducible builds, you must do the following:

  • Pass -trimpath to the Go compiler.

  • For the following platforms, also pass -buildmode=pie to the Go compiler:

    • GOOS=windows, any GOARCH

    • GOOS=linux, GOARCH=amd64 or GOARCH=arm64

  • Disable cgo by setting the CGO_ENABLED environment variable to 0.

  • Follow the requirements above for putting accurate version information into the binary, so that the user is able to uniquely identify the build by running elvish -version.

    The recommendation for how to set VersionSuffix when packaging development builds becomes hard requirements when packaging reproducible builds.

    In addition, if your distribution uses a patched version of the Go compiler that changes its output, or if the build command uses any additional flags (either via the command line or via any environment variables), you must treat this as a patch on Elvish itself, and supply a version suffix accordingly.

If you follow these requirements when building Elvish, you can mark the build as a reproducible one by overriding github.com/markusbkk/elvish/pkg/buildinfo.Reproducible to "true".

Example when building a release version without any patches, on a platform where PIE is applicable:

go build -buildmode=pie -trimpath \
  -ldflags "-X github.com/markusbkk/elvish/pkg/buildinfo.Reproducible=true" \
  ./cmd/elvish

Example when building a development version with a patch, on a platform where PIE is application:

go build -buildmode=pie -trimpath \
  -ldflags "-X github.com/markusbkk/elvish/pkg/buildinfo.VersionSuffix=-dev.$(git rev-parse HEAD)+deb0 \
            -X github.com/markusbkk/elvish/pkg/buildinfo.Reproducible=true" \
  ./cmd/elvish