build: check for outputs in --if-newer check (RHBZ#1813809)

In case we need to check whether the appliance must be rebuilt, check
also the timestamp of the outputs of the mode, i.e. the kernel, initrd,
and root files. This way, when either of these files does not exist or
is older than the package manager DB we can rebuild the appliance.

Add a simple test to verify this behaviour.

src/mode_build.ml

@@ -462,3 +462,15 @@ and munge files =
   let files = loop files in
 
   files
+
+and get_outputs
+    (copy_kernel, format, host_cpu,
+     packager_config, tmpdir, use_installed, size,
+     include_packagelist)
+    inputs =
+  match format with
+  | Chroot ->
+    (* The content for chroot depends on the packages. *)
+    []
+  | Ext2 ->
+    [kernel_filename; appliance_filename; initrd_filename]

src/mode_build.mli

@@ -21,3 +21,7 @@
 val build : int -> (bool * Types.format * string * string option * string * bool * int64 option * bool) -> string list -> string -> unit
 (** [build debug (args...) inputs outputdir] performs the
     [supermin --build] subcommand. *)
+
+val get_outputs : (bool * Types.format * string * string option * string * bool * int64 option * bool) -> string list -> string list
+(** [get_outputs (args...) inputs] gets the potential outputs for the
+    appliance. *)

src/supermin.ml

@@ -236,10 +236,12 @@ appliance automatically.
    *)
   if mode = Build && if_newer then (
     try
-      let odate = (lstat outputdir).st_mtime in
+      let outputs = Mode_build.get_outputs args inputs in
+      let outputs = List.map ((//) outputdir) outputs in
+      let odates = List.map (fun d -> (lstat d).st_mtime) (outputdir :: outputs) in
       let idates = List.map (fun d -> (lstat d).st_mtime) inputs in
       let pdate = (get_package_handler ()).ph_get_package_database_mtime () in
-      if List.for_all (fun idate -> idate < odate) (pdate :: idates) then (
+      if List.for_all (fun idate -> List.for_all (fun odate -> idate < odate) odates) (pdate :: idates) then (
         if debug >= 1 then
           printf "supermin: if-newer: output does not need rebuilding\n%!";
         exit 0

tests/Makefile.am

@@ -28,7 +28,8 @@ TESTS = \
 	test-execstack.sh \
 	test-build-bash.sh \
 	test-binaries-exist.sh \
-	test-harder.sh
+	test-harder.sh \
+	test-if-newer-ext2.sh
 
 if NETWORK_TESTS
 TESTS += \

tests/test-if-newer-ext2.sh

@@ -0,0 +1,57 @@
+#!/bin/bash -
+# supermin
+# (C) Copyright 2009-2020 Red Hat Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+set -e
+
+# XXX Hack for Arch.
+if [ -f /etc/arch-release ]; then
+    export SUPERMIN_KERNEL=/boot/vmlinuz-linux
+fi
+
+tmpdir=`mktemp -d`
+
+d1=$tmpdir/d1
+d2=$tmpdir/d2
+
+# We assume 'bash' is a package everywhere.
+../src/supermin -v --prepare --use-installed bash -o $d1
+
+run_supermin ()
+{
+  ../src/supermin -v --build -f ext2 --if-newer $d1 -o $d2
+}
+
+# Build the appliance the first time, which will work.
+run_supermin
+
+# No changes, hence nothing to do.
+run_supermin | grep 'if-newer: output does not need rebuilding'
+
+# Try removing any of the files, and check that supermin will detect that.
+ext2_files="kernel initrd root"
+for ext2_file in $ext2_files
+do
+  rm $d2/$ext2_file
+  run_supermin
+  for ext2_file in $ext2_files
+  do
+    test -e $d2/$ext2_file
+  done
+done
+
+rm -rf $tmpdir ||: