Bazel tar rule

General-purpose rule to create tar archives.

Unlike pkg_tar from rules_pkg:

• It does not depend on any Python interpreter setup
• The "manifest" specification is a mature public API and uses a compact tabular format, fixing bazelbuild/rules_pkg#238
• It doesn't rely custom program to produce the output, instead we rely on the well-known C++ program tar(1). Specifically, we use the BSD variant of tar since it provides a means of controlling mtimes, uid, symlinks, etc.

We also provide full control for tar'ring binaries including their runfiles.

The tar binary is hermetic and fully statically-linked. See Design Notes below.

This rule was originally developed within bazel-lib. Thanks to all the contributors who made it possible!

Simplest possible usage:

load("@tar.bzl", "tar")

# build this target to produce archive.tar
tar(
    name = "archive",
    srcs = ["my-file.txt"],
)

Mutations allow modification of the archive's structure. For example to strip the package name:

load("@tar.bzl", "mutate", "tar")

tar(
    name = "new",
    srcs = ["my-file.txt"],
    # See arguments documented at
    # https://github.com/bazel-contrib/tar.bzl/blob/main/docs/mtree.md#mtree_mutate
    mutate = mutate(strip_prefix = package_name()),
)

Other examples:

• Migrate from pkg_tar: https://github.com/bazel-contrib/tar.bzl/blob/main/examples/migrate-rules_pkg/BUILD
• Look through our test suite: https://github.com/bazel-contrib/tar.bzl/blob/main/tar/tests/BUILD

Note; this repository doesn't yet allow modes other than create, such as "append", "list", "update", "extract". See https://registry.bazel.build/modules/rules_tar for this.

• tar Run BSD tar(1) to produce archives
• mtree The intermediate manifest format mtree(8) describing a tar operation

1. We start from libarchive, which is on the BCR: https://registry.bazel.build/modules/libarchive
2. You could choose to register a toolchain that builds from source, but most users want a pre-built tar binary: https://github.com/aspect-build/bsdtar-prebuilt
3. bazel-lib defines the toolchain type, and registers a sensible default toolchain: https://github.com/bazel-contrib/bazel-lib/blob/main/lib/private/tar_toolchain.bzl
4. This repo then contains just the starlark rule code for invoking tar within Bazel actions (aka. build steps)