feat: add a tar toolchain (#468)

* feat: add a BSD tar toolchain

@thesayyn discovered that it has a feature which should make it a drop-in replacement for pkg_tar
including fine-grained file permissions and symlinks:
https://man.freebsd.org/cgi/man.cgi?mtree(8)

* show example of mtree usage

* feat: introduce tar rule

* cleanup and get test passing

* more cleanup

* chore: add support for compress flags

* chore: add docs

* chore: add docs

* feat: implement linux bsdtar toolchain (#566)

* chore: improve target naming

* WIP: args

* feat: generate mtree spec

Also allow arbitrary args

* refactor: mtree is required

* refactor: style nits

* fix: support mix of source and generated artifacts

* feat: demonstrate strip_prefix

* chore: regen docs

* fix: make host toolchain a fallback toolchain

* fix: include libarchive13.so when installing BSD tar

* chore: buildifier

* fix: aarch64 cpu constraint

* fix(ci): include libarchive13.so when running tar

* chore: add libnettle

* refactor: inputs mutated less

* refactor: remove unneeded substitution arg

* refactor: don't advertise unsupported modes

* fix: hack enough to make it run on my machine

* chore: dynamic libraries included in sh_binary under toolchain

* make sh_binary work

* refactor: drop arm64 for now

* fix toolchain

* fix test

* chore: improve test naming scheme

---------

Co-authored-by: Sahin Yort <thesayyn@gmail.com>

docs/BUILD.bazel

@@ -59,6 +59,11 @@ stardoc_with_diff_test(
     bzl_library_target = "//lib:lists",
 )
 
+stardoc_with_diff_test(
+    name = "tar",
+    bzl_library_target = "//lib:tar",
+)
+
 stardoc_with_diff_test(
     name = "utils",
     bzl_library_target = "//lib:utils",

internal_deps.bzl

@@ -4,7 +4,7 @@ Users should *not* need to install these. If users see a load()
 statement from these, that's a bug in our distribution.
 """
 
-load("//lib:repositories.bzl", "register_coreutils_toolchains", "register_jq_toolchains", "register_yq_toolchains")
+load("//lib:repositories.bzl", "register_coreutils_toolchains", "register_jq_toolchains", "register_tar_toolchains", "register_yq_toolchains")
 load("//lib:utils.bzl", http_archive = "maybe_http_archive")
 
 # buildifier: disable=unnamed-macro
@@ -73,3 +73,4 @@ def bazel_lib_internal_deps():
     register_jq_toolchains()
     register_yq_toolchains()
     register_coreutils_toolchains()
+    register_tar_toolchains()

lib/BUILD.bazel

@@ -79,6 +79,10 @@ toolchain_type(
     name = "expand_template_toolchain_type",
 )
 
+toolchain_type(
+    name = "tar_toolchain_type",
+)
+
 bzl_library(
     name = "docs",
     srcs = ["docs.bzl"],
@@ -125,6 +129,16 @@ bzl_library(
     deps = ["//lib/private/docs:utils"],
 )
 
+bzl_library(
+    name = "tar",
+    srcs = ["tar.bzl"],
+    deps = [
+        "//lib/private/docs:tar",
+        "@bazel_skylib//lib:types",
+        "@bazel_skylib//rules:write_file",
+    ],
+)
+
 bzl_library(
     name = "jq",
     srcs = ["jq.bzl"],
@@ -260,6 +274,7 @@ bzl_library(
         "//lib/private/docs:jq_toolchain",
         "//lib/private/docs:local_config_platform",
         "//lib/private/docs:source_toolchains_repo",
+        "//lib/private/docs:tar_toolchain",
         "//lib/private/docs:yq_toolchain",
     ],
 )

lib/extensions.bzl

@@ -9,13 +9,15 @@ load(
     "DEFAULT_EXPAND_TEMPLATE_REPOSITORY",
     "DEFAULT_JQ_REPOSITORY",
     "DEFAULT_JQ_VERSION",
+    "DEFAULT_TAR_REPOSITORY",
     "DEFAULT_YQ_REPOSITORY",
     "DEFAULT_YQ_VERSION",
     "register_copy_directory_toolchains",
     "register_copy_to_directory_toolchains",
     "register_coreutils_toolchains",
     "register_expand_template_toolchains",
     "register_jq_toolchains",
+    "register_tar_toolchains",
     "register_yq_toolchains",
 )
 load("//lib/private:extension_utils.bzl", "extension_utils")
@@ -27,6 +29,7 @@ def _toolchain_extension(mctx):
     register_jq_toolchains(register = False)
     register_yq_toolchains(register = False)
     register_coreutils_toolchains(register = False)
+    register_tar_toolchains(register = False)
     register_expand_template_toolchains(register = False)
 
     create_host_repo = False
@@ -101,6 +104,15 @@ def _toolchains_extension_impl(mctx):
         toolchain_repos_fn = lambda name, version: register_coreutils_toolchains(name = name, version = version, register = False),
     )
 
+    extension_utils.toolchain_repos_bfs(
+        mctx = mctx,
+        get_tag_fn = lambda tags: tags.tar,
+        toolchain_name = "tar",
+        default_repository = DEFAULT_TAR_REPOSITORY,
+        toolchain_repos_fn = lambda name, version: register_tar_toolchains(name = name, register = False),
+        get_version_fn = lambda attr: None,
+    )
+
     extension_utils.toolchain_repos_bfs(
         mctx = mctx,
         get_tag_fn = lambda tags: tags.expand_template,
@@ -117,6 +129,7 @@ toolchains = module_extension(
         "jq": tag_class(attrs = {"name": attr.string(default = DEFAULT_JQ_REPOSITORY), "version": attr.string(default = DEFAULT_JQ_VERSION)}),
         "yq": tag_class(attrs = {"name": attr.string(default = DEFAULT_YQ_REPOSITORY), "version": attr.string(default = DEFAULT_YQ_VERSION)}),
         "coreutils": tag_class(attrs = {"name": attr.string(default = DEFAULT_COREUTILS_REPOSITORY), "version": attr.string(default = DEFAULT_COREUTILS_VERSION)}),
+        "tar": tag_class(attrs = {"name": attr.string(default = DEFAULT_TAR_REPOSITORY)}),
         "expand_template": tag_class(attrs = {"name": attr.string(default = DEFAULT_EXPAND_TEMPLATE_REPOSITORY)}),
     },
 )

lib/private/docs/BUILD.bazel

@@ -121,6 +121,13 @@ bzl_library(
     ],
 )
 
+bzl_library(
+    name = "tar",
+    srcs = [
+        "//lib/private:tar.bzl",
+    ],
+)
+
 bzl_library(
     name = "utils",
     srcs = [
@@ -211,6 +218,12 @@ bzl_library(
     deps = [":repo_utils"],
 )
 
+bzl_library(
+    name = "tar_toolchain",
+    srcs = ["//lib/private:tar_toolchain.bzl"],
+    deps = [":repo_utils"],
+)
+
 bzl_library(
     name = "repo_utils",
     srcs = ["//lib/private:repo_utils.bzl"],