bootc-base-imagectl: support extending package list

The current custom base image flow of rebuilding a "built-in" image with
custom repos and then adding your own content separate is reasonable,
but it would be nice if one could augment the list of packages to
install in that initial build rather than as a separate transaction.

Then, you don't have to cleanup after dnf and `/var` content, re-inject
repo definitions, and refetch repo metadata. It also allows building
container images with additional packages without `dnf` necessarily
being in the package set.

We don't want to leak rpm-ostree implementation details, nor do we want
to invent a new format. So just add support for a `--install` arg and a
generic `--args-file` to pass arguments via a file.

We then generate a new treefile on the fly to extend the `packages`
list.

bootc-base-imagectl

@@ -8,6 +8,7 @@ import stat
 import json
 import argparse
 import sys
+import tempfile
 
 MANIFESTDIR = 'usr/share/doc/bootc-base-imagectl/manifests'
 
@@ -17,9 +18,23 @@ def run_build_rootfs(args):
     """
     target = args.target
     if os.path.isdir(args.manifest):
-        manifest_path = os.path.join(args.manifest, 'manifest.yaml')
+        manifest_path = os.path.join(f'/{MANIFESTDIR}', args.manifest, 'manifest.yaml')
     else:
-        manifest_path = args.manifest + '.yaml'
+        manifest_path = f'/{MANIFESTDIR}/{args.manifest}.yaml'
+
+    tmp_manifest = None
+    if args.install:
+        additional_pkgs = set(args.install)
+        if len(additional_pkgs) > 0:
+            final_manifest = {
+                "include": manifest_path,
+                "packages": list(additional_pkgs),
+            }
+            tmp_manifest = tempfile.NamedTemporaryFile(mode='w', encoding='utf-8', suffix='.json', delete_on_close=False)
+            json.dump(final_manifest, tmp_manifest)
+            tmp_manifest.close()
+            manifest_path = tmp_manifest.name
+
     rpmostree_argv = ['rpm-ostree', 'compose', 'rootfs']
     try:
         # Assume we can mutate alternative roots
@@ -28,7 +43,7 @@ def run_build_rootfs(args):
         else:
             # But we shouldn't need to mutate the default root
             rpmostree_argv.append('--source-root=/')
-        rpmostree_argv.extend([f'/{MANIFESTDIR}/{manifest_path}', target])
+        rpmostree_argv.extend([manifest_path, target])
         # Perform the build
         subprocess.run(rpmostree_argv, check=True)
         # Work around https://github.com/coreos/rpm-ostree/pull/5322
@@ -46,6 +61,9 @@ def run_build_rootfs(args):
     except subprocess.CalledProcessError as e:
         print(f"Error executing command: {e}")
         sys.exit(1)
+    finally:
+        if tmp_manifest is not None:
+            del tmp_manifest
 
     # Copy our own build configuration into the target if configured;
     # this is used for the first stage build. But by default *secondary*
@@ -95,11 +113,13 @@ def run_list(args):
 
 if __name__ == "__main__":
     parser = argparse.ArgumentParser(description="Operate on the build configuration for this container")
+    parser.add_argument("--args-file", help="File containing arguments to parse (one argument per line)", metavar='FILE')
     subparsers = parser.add_subparsers(help='Subcommands', required=True)
 
     build_rootfs = subparsers.add_parser('build-rootfs', help='Generate a container root filesystem')
     build_rootfs.add_argument("--reinject", help="Also reinject the build configurations into the target", action='store_true')
     build_rootfs.add_argument("--manifest", help="Use the specified manifest", action='store', default='default')
+    build_rootfs.add_argument("--install", help="Add a package", action='append', default=[], metavar='PACKAGE')
     build_rootfs.add_argument("source_root", help="Path to the source root directory used for dnf configuration (default=/)", nargs='?', default='/')
     build_rootfs.add_argument("target", help="Path to the target root directory that will be generated.")
     build_rootfs.set_defaults(func=run_build_rootfs)
@@ -114,5 +134,12 @@ if __name__ == "__main__":
     cmd_list.set_defaults(func=run_list)
 
     args = parser.parse_args()
+    if args.args_file:
+        add_args = []
+        with open(args.args_file) as f:
+            for line in f:
+                add_args += [line.strip()]
+        args = parser.parse_args(sys.argv[1:] + add_args)
+
     args.func(args)
 

tests/Containerfile.test-derive

@@ -5,7 +5,10 @@ FROM quay.io/fedora/fedora-bootc:rawhide as repos
 
 # This is intentionally a locally built image
 FROM localhost/fedora-bootc as builder
-RUN --mount=type=bind,from=repos,src=/,dst=/repos,rw /usr/libexec/bootc-base-imagectl build-rootfs --manifest=standard/manifest /repos /target-rootfs
+RUN --mount=type=bind,from=repos,src=/,dst=/repos,rw <<EORUN
+echo -e '--install\nltrace' > args.txt
+/usr/libexec/bootc-base-imagectl --args-file args.txt build-rootfs --manifest=standard/manifest /repos /target-rootfs
+EORUN
 
 # This pulls in the rootfs generated in the previous step
 FROM scratch
@@ -15,6 +18,8 @@ set -xeuo pipefail
 . /usr/lib/os-release
 test "$ID" = fedora
 
+rpm -q ltrace
+
 # And install a package
 dnf -y install strace
 dnf clean all