app/db-diff: assume booted deployment if less args

Very often when I have a pending deployment, I just want to find out
what the diff is before rebooting. We do print it after whatever
transaction laid down the new deployment, though we may not reboot right
away. It seems like a common enough operation to warrant some shortcuts.

This makes `db diff` more useful by automatically subbing in the booted
deployment if less arguments are given:

    rpm-ostree db diff
      <diff booted and pending deployment>
    rpm-ostree db diff $csum
      <diff booted and $csum>
    rpm-ostree db diff $csum1 $csum2
      <as before, diff $csum1 and $csum2>

As before, we never try to even load the sysroot in the last invocation,
so it still works equally well on non-OSTree systems/unprivileged.

Closes: #1294
Approved by: cgwalters

man/rpm-ostree.xml

@@ -137,7 +137,10 @@ Boston, MA 02111-1307, USA.
 
           <para>
             <command>diff</command> to see how the packages are
-            different between the trees in two commits.  The
+            different between the trees in two revs. If no revs are
+            provided, the booted commit is compared to the pending
+            commit. If only a single rev is provided, the booted commit
+            is compared to that rev. The
             <option>--format=diff</option> option uses
             <literal>-</literal> for removed packages,
             <literal>+</literal> for added packages, and finally

src/app/rpmostree-db-builtin-diff.c

@@ -27,10 +27,12 @@
 
 static char *opt_format = "block";
 static gboolean opt_changelogs;
+static char *opt_sysroot;
 
 static GOptionEntry option_entries[] = {
   { "format", 'F', 0, G_OPTION_ARG_STRING, &opt_format, "Output format: \"diff\" or (default) \"block\"", "FORMAT" },
   { "changelogs", 'c', 0, G_OPTION_ARG_NONE, &opt_changelogs, "Also output RPM changelogs", NULL },
+  { "sysroot", 0, 0, G_OPTION_ARG_STRING, &opt_sysroot, "Use system root SYSROOT (default: /)", "SYSROOT" },
   { NULL }
 };
 
@@ -96,32 +98,73 @@ rpmostree_db_builtin_diff (int argc, char **argv,
                            RpmOstreeCommandInvocation *invocation,
                            GCancellable *cancellable, GError **error)
 {
-  g_autoptr(GOptionContext) context = g_option_context_new ("COMMIT COMMIT");
+  g_autoptr(GOptionContext) context = g_option_context_new ("[FROM_REV] [TO_REV]");
 
   g_autoptr(OstreeRepo) repo = NULL;
   if (!rpmostree_db_option_context_parse (context, option_entries, &argc, &argv, invocation,
                                           &repo, cancellable, error))
     return FALSE;
 
-  if (argc != 3)
+  if (argc > 3)
     {
       g_autofree char *message =
-        g_strdup_printf ("\"%s\" takes exactly 2 arguments", g_get_prgname ());
+        g_strdup_printf ("\"%s\" takes at most 2 arguments", g_get_prgname ());
       rpmostree_usage_error (context, message, error);
       return FALSE;
     }
 
-  const char *old_ref = argv[1];
+  const char *old_desc = NULL;
   g_autofree char *old_checksum = NULL;
-  if (!ostree_repo_resolve_rev (repo, old_ref, FALSE, &old_checksum, error))
-    return FALSE;
-
-  const char *new_ref = argv[2];
+  const char *new_desc = NULL;
   g_autofree char *new_checksum = NULL;
-  if (!ostree_repo_resolve_rev (repo, new_ref, FALSE, &new_checksum, error))
-    return FALSE;
 
-  return print_diff (repo, old_ref, old_checksum, new_ref, new_checksum,
+  if (argc < 3)
+    {
+      /* find booted deployment */
+      const char *sysroot_path = opt_sysroot ?: "/";
+      g_autoptr(GFile) sysroot_file = g_file_new_for_path (sysroot_path);
+      g_autoptr(OstreeSysroot) sysroot = ostree_sysroot_new (sysroot_file);
+      if (!ostree_sysroot_load (sysroot, cancellable, error))
+        return FALSE;
+
+      OstreeDeployment *booted = ostree_sysroot_get_booted_deployment (sysroot);
+      if (!booted)
+        return glnx_throw (error, "Not booted into any deployment");
+
+      old_desc = "booted deployment";
+      old_checksum = g_strdup (ostree_deployment_get_csum (booted));
+
+      if (argc < 2)
+        {
+          /* diff booted against pending deployment */
+          new_desc = "pending deployment";
+          g_autoptr(OstreeDeployment) pending = NULL;
+          ostree_sysroot_query_deployments_for (sysroot, NULL, &pending, NULL);
+          if (!pending || ostree_deployment_equal (pending, booted))
+            return glnx_throw (error, "No pending deployment to diff against");
+          new_checksum = g_strdup (ostree_deployment_get_csum (pending));
+        }
+      else
+        {
+          /* diff against the booted deployment */
+          new_desc = argv[1];
+          if (!ostree_repo_resolve_rev (repo, new_desc, FALSE, &new_checksum, error))
+            return FALSE;
+        }
+    }
+  else
+    {
+      old_desc = argv[1];
+      if (!ostree_repo_resolve_rev (repo, old_desc, FALSE, &old_checksum, error))
+        return FALSE;
+
+      new_desc = argv[2];
+      if (!ostree_repo_resolve_rev (repo, new_desc, FALSE, &new_checksum, error))
+        return FALSE;
+
+    }
+
+  return print_diff (repo, old_desc, old_checksum, new_desc, new_checksum,
                      cancellable, error);
 }
 

tests/vmcheck/test-db.sh

@@ -30,9 +30,16 @@ set -x
 YUMREPO=/tmp/vmcheck/yumrepo/packages/x86_64
 
 check_diff() {
-  from=$1; shift
-  to=$1; shift
-  vm_rpmostree db diff --format=diff $from $to > diff.txt
+  arg1=$1; shift
+  arg2=$1; shift
+  cmd="vm_rpmostree db diff --format=diff"
+  if [ -n "$arg1" ]; then
+    cmd="$cmd $arg1"
+  fi
+  if [ -n "$arg2" ]; then
+    cmd="$cmd $arg2"
+  fi
+  $cmd > diff.txt
   assert_file_has_content diff.txt "$@"
 }
 
@@ -55,6 +62,18 @@ check_diff $booted_csum $pending_csum \
   +pkg-to-replace \
   +pkg-to-replace-archtrans
 
+# check that it's the default behaviour without both args
+check_diff "" "" \
+  +pkg-to-remove \
+  +pkg-to-replace \
+  +pkg-to-replace-archtrans
+
+# check that it's the default behaviour without one arg
+check_diff "$pending_csum" "" \
+  +pkg-to-remove \
+  +pkg-to-replace \
+  +pkg-to-replace-archtrans
+
 # now let's make the pending csum become an update
 vm_cmd ostree commit -b vmcheck --tree=ref=$pending_csum
 vm_rpmostree cleanup -p