ostree admin instutil set-kargs: make more flexible

Add command line arguments:
 --import-proc-cmdline: import values from /proc/cmdline
 --merge: import current values
 --replace=ARG=VALUE: replace value
 --append=ARG=VALUE: append a new argument

Extra command line arguments are treated like --append=, which
gives backwards compatibility.

https://bugzilla.gnome.org/show_bug.cgi?id=731051

src/libostree/ostree-kernel-args.c

@@ -21,6 +21,7 @@
 #include "config.h"
 
 #include "ostree-kernel-args.h"
+#include "libgsystem.h"
 
 #include <string.h>
 
@@ -156,6 +157,29 @@ _ostree_kernel_args_append_argv (OstreeKernelArgs  *kargs,
     }
 }
 
+gboolean
+_ostree_kernel_args_append_proc_cmdline (OstreeKernelArgs *kargs,
+                                         GCancellable     *cancellable,
+                                         GError          **error)
+{
+  gs_unref_object GFile *proc_cmdline_path = g_file_new_for_path ("/proc/cmdline");
+  gs_free char *proc_cmdline = NULL;
+  gsize proc_cmdline_len = 0;
+  gs_strfreev char **proc_cmdline_args = NULL;
+
+  if (!g_file_load_contents (proc_cmdline_path, cancellable,
+                             &proc_cmdline, &proc_cmdline_len,
+                             NULL, error))
+    return FALSE;
+
+  g_strchomp (proc_cmdline);
+
+  proc_cmdline_args = g_strsplit (proc_cmdline, " ", -1);
+  _ostree_kernel_args_append_argv (kargs, proc_cmdline_args);
+
+  return TRUE;
+}
+
 void
 _ostree_kernel_args_parse_append (OstreeKernelArgs *kargs,
                                   const char       *options)

src/libostree/ostree-kernel-args.h

@@ -40,6 +40,10 @@ void _ostree_kernel_args_append (OstreeKernelArgs  *kargs,
 void _ostree_kernel_args_append_argv (OstreeKernelArgs  *kargs,
                                       char **argv);
 
+gboolean _ostree_kernel_args_append_proc_cmdline (OstreeKernelArgs *kargs,
+                                                  GCancellable     *cancellable,
+                                                  GError          **error);
+
 void _ostree_kernel_args_parse_append (OstreeKernelArgs *kargs,
                                        const char *options);