lib/checkout: Rename disjoint union, change to merge identical files

It turns out that librpm automatically merges identical files between
distinct packages, and this occurs in practice with Fedora today between
`chkconfig` and `initscripts` for exmaple.

Since we added this for rpm-ostree, we basically want to do what librpm does,
let's change the semantics to do a merge.  While we're here rename
to `UNION_IDENTICAL`.

Closes: #1156
Approved by: jlebon

1 files changed, 17 insertions, 9 deletions

diff --git a/src/ostree/ot-builtin-checkout.c b/src/ostree/ot-builtin-checkout.c
index a3494ae3..170d24e9 100644
--- a/src/ostree/ot-builtin-checkout.c
+++ b/src/ostree/ot-builtin-checkout.c
@@ -37,7 +37,7 @@ static gboolean opt_disable_cache;
 static char *opt_subpath;
 static gboolean opt_union;
 static gboolean opt_union_add;
-static gboolean opt_disjoint_union;
+static gboolean opt_union_identical;
 static gboolean opt_whiteouts;
 static gboolean opt_from_stdin;
 static char *opt_from_file;
@@ -73,7 +73,7 @@ static GOptionEntry options[] = {
   { "subpath", 0, 0, G_OPTION_ARG_FILENAME, &opt_subpath, "Checkout sub-directory PATH", "PATH" },
   { "union", 0, 0, G_OPTION_ARG_NONE, &opt_union, "Keep existing directories, overwrite existing files", NULL },
   { "union-add", 0, 0, G_OPTION_ARG_NONE, &opt_union_add, "Keep existing files/directories, only add new", NULL },
-  { "disjoint-union", 0, 0, G_OPTION_ARG_NONE, &opt_disjoint_union, "When layering checkouts, error out if a file would be replaced, but add new files and directories", NULL },
+  { "union-identical", 0, 0, G_OPTION_ARG_NONE, &opt_union_identical, "When layering checkouts, error out if a file would be replaced with a different version, but add new files and directories", NULL },
   { "whiteouts", 0, 0, G_OPTION_ARG_NONE, &opt_whiteouts, "Process 'whiteout' (Docker style) entries", NULL },
   { "allow-noent", 0, 0, G_OPTION_ARG_NONE, &opt_allow_noent, "Do nothing if specified path does not exist", NULL },
   { "from-stdin", 0, 0, G_OPTION_ARG_NONE, &opt_from_stdin, "Process many checkouts from standard input", NULL },
@@ -101,7 +101,7 @@ process_one_checkout (OstreeRepo           *repo,
    * convenient infrastructure for testing C APIs with data.
    */
   if (opt_disable_cache || opt_whiteouts || opt_require_hardlinks ||
-      opt_union_add || opt_force_copy || opt_bareuseronly_dirs || opt_disjoint_union)
+      opt_union_add || opt_force_copy || opt_bareuseronly_dirs || opt_union_identical)
     {
       OstreeRepoCheckoutAtOptions options = { 0, };
 
@@ -114,16 +114,16 @@ process_one_checkout (OstreeRepo           *repo,
                        "Cannot specify both --union and --union-add");
           goto out;
         }
-      if (opt_union && opt_disjoint_union)
+      if (opt_union && opt_union_identical)
         {
           g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
-                       "Cannot specify both --union and --disjoint-union");
+                       "Cannot specify both --union and --union-identical");
           goto out;
         }
-      if (opt_union_add && opt_disjoint_union)
+      if (opt_union_add && opt_union_identical)
         {
           g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
-                       "Cannot specify both --union-add and --disjoint-union ");
+                       "Cannot specify both --union-add and --union-identical ");
           goto out;
         }
       if (opt_require_hardlinks && opt_force_copy)
@@ -135,8 +135,16 @@ process_one_checkout (OstreeRepo           *repo,
         options.overwrite_mode = OSTREE_REPO_CHECKOUT_OVERWRITE_UNION_FILES;
       else if (opt_union_add)
         options.overwrite_mode = OSTREE_REPO_CHECKOUT_OVERWRITE_ADD_FILES;
-      else if (opt_disjoint_union)
-        options.overwrite_mode = OSTREE_REPO_CHECKOUT_OVERWRITE_DISJOINT_UNION_FILES;
+      else if (opt_union_identical)
+        {
+          if (!opt_require_hardlinks)
+            {
+              g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
+                           "--union-identical requires --require-hardlinks");
+              goto out;
+            }
+          options.overwrite_mode = OSTREE_REPO_CHECKOUT_OVERWRITE_UNION_IDENTICAL;
+        }
       if (opt_whiteouts)
         options.process_whiteouts = TRUE;
       if (subpath)