Minimize the number of manually installed packages in images by marking

dependencies of metapackages as automatically installed.

debian/changelog

@@ -1,3 +1,10 @@
+livecd-rootfs (2.536ubuntu1) UNRELEASED; urgency=medium
+
+  * Minimize the number of manually installed packages in images by marking
+    dependencies of metapackages as automatically installed.
+
+ -- Julian Andres Klode <juliank@ubuntu.com>  Tue, 18 Sep 2018 08:55:04 +0200
+
 livecd-rootfs (2.536) cosmic; urgency=medium
 
   * Fix live-server journald config snippet to actually disable journald rate

debian/control

@@ -26,6 +26,7 @@ Depends: ${misc:Depends},
          parted,
          procps,
          python-minimal | python,
+         python3-apt,
          python3-software-properties,
          qemu-utils,
          rsync,

live-build/auto/build

@@ -445,6 +445,8 @@ EOF
 	(cd chroot && find usr/share/doc -maxdepth 1 -type d | xargs du -s | sort -nr)
 	echo END docdirs
 
+	live-build/auto/minimize-manual.py chroot
+
 	lb binary "$@"
 	touch binary.success
 ) 2>&1 | tee binary.log

live-build/auto/minimize-manual.py

@@ -0,0 +1,48 @@
+#!/usr/bin/python3
+"""Minimize the number of manually installed packages in the image.
+
+Finds all manually meta packages and marks their dependencies as
+automatically installed.
+"""
+import apt
+import sys
+
+
+def is_root(pkg):
+    return (pkg.is_installed and
+            not pkg.is_auto_installed and
+            (pkg.section == "metapackages" or
+             pkg.section.endswith("/metapackages")))
+
+
+c = apt.Cache(rootdir=sys.argv[1] if len(sys.argv) > 1 else None)
+
+roots = set(pkg for pkg in c if is_root(pkg))
+workset = set(roots)
+seen = set()
+
+with c.actiongroup():
+    while True:
+
+        print("Iteration", file=sys.stderr)
+        to_proc = workset - seen
+        if not to_proc:
+            break
+        for pkg in sorted(to_proc):
+            print("    Visiting", pkg, file=sys.stderr)
+
+            # Mark every
+            if pkg not in roots:
+                pkg.mark_auto()
+
+            for dep in pkg.installed.dependencies + pkg.installed.recommends:
+                if dep.rawtype not in ('Depends', 'PreDepends', 'Recommends'):
+                    continue
+                for bdep in dep.or_dependencies:
+                    for v in bdep.target_versions:
+                        if v.package.is_installed:
+                            workset.add(v.package)
+
+            seen.add(pkg)
+
+    c.commit()