compose: Make boot_location: legacy be an alias for both

We have 3 locations to find kernels now; I can't think of
a reason to support placing kernels *only* in `/boot`.  The
original commit
15ecaac
doesn't give a reason, and I certainly can't think of one now.

This makes `legacy` be an alias for `both`, which should be fully compatible.

Prep for further refactoring towards changing `new` to mean both
`/usr/lib/ostree-boot` *and* `/usr/lib/modules`.

Closes: #959
Approved by: jlebon

docs/manual/treefile.md

@@ -30,8 +30,8 @@ It supports the following parameters:
     in /boot.  However, this has a few flaws; it gets shadowed at boot time,
     and also makes dealing with Anaconda installation harder.  There are 3
     possible values:
-    * "legacy": kernel data goes in /boot
     * "both": the default, kernel data goes in /boot and /usr/lib/ostree-boot
+    * "legacy": Now an alias for "both"; historically meant just "boot"
     * "new": kernel data goes in /usr/lib/ostree-boot
 
  * `etc-group-members`: Array of strings, optional: Unix groups in this

src/libpriv/rpmostree-postprocess.c

@@ -46,7 +46,6 @@
 #include "rpmostree-util.h"
 
 typedef enum {
-  RPMOSTREE_POSTPROCESS_BOOT_LOCATION_LEGACY,
   RPMOSTREE_POSTPROCESS_BOOT_LOCATION_BOTH,
   RPMOSTREE_POSTPROCESS_BOOT_LOCATION_NEW
 } RpmOstreePostprocessBootLocation;
@@ -801,9 +800,9 @@ create_rootfs_from_pkgroot_content (int            target_root_dfd,
 
       if (boot_location_str != NULL)
         {
-          if (strcmp (boot_location_str, "legacy") == 0)
-            boot_location = RPMOSTREE_POSTPROCESS_BOOT_LOCATION_LEGACY;
-          else if (strcmp (boot_location_str, "both") == 0)
+          /* Note that "legacy" is now an alias for "both" */
+          if (strcmp (boot_location_str, "both") == 0 ||
+              strcmp (boot_location_str, "legacy") == 0)
             boot_location = RPMOSTREE_POSTPROCESS_BOOT_LOCATION_BOTH;
           else if (strcmp (boot_location_str, "new") == 0)
             boot_location = RPMOSTREE_POSTPROCESS_BOOT_LOCATION_NEW;
@@ -817,13 +816,6 @@ create_rootfs_from_pkgroot_content (int            target_root_dfd,
 
       switch (boot_location)
         {
-        case RPMOSTREE_POSTPROCESS_BOOT_LOCATION_LEGACY:
-          {
-            g_print ("Using boot location: legacy\n");
-            if (!glnx_renameat (src_rootfs_fd, "boot", target_root_dfd, "boot", error))
-              return FALSE;
-          }
-          break;
         case RPMOSTREE_POSTPROCESS_BOOT_LOCATION_BOTH:
           {
             g_print ("Using boot location: both\n");