If new and old repomd matches during --update don't update

If the repomd matches it contains the same data. By not touching the
repodata files we can potentially save resources because other tools
don't have to evaluate the files for changes.

= changelog =
msg: If the new repodata generated during an --update run exactly matches the old repodata don't touch the files.
type: enhancement

1 files changed, 32 insertions, 13 deletions

diff --git a/src/createrepo_c.c b/src/createrepo_c.c
index 202ff0d..79db08a 100644
--- a/src/createrepo_c.c
+++ b/src/createrepo_c.c
@@ -45,6 +45,7 @@
 #include "misc.h"
 #include "parsepkg.h"
 #include "repomd.h"
+#include "repomd_internal.h"
 #include "sqlite.h"
 #include "threads.h"
 #include "version.h"
@@ -949,9 +950,6 @@ main(int argc, char **argv)
         }
     }
 
-    cr_metadatalocation_free(old_metadata_location);
-    old_metadata_location = NULL;
-
     // Create and open new compressed files
     cr_XmlFile *pri_cr_file;
     cr_XmlFile *fil_cr_file;
@@ -1981,9 +1979,24 @@ deltaerror:
 
     cr_repomd_sort_records(repomd_obj);
 
+
+    // Compare old repomd with the new one to see if we actually need to update the repodata.
+    // If some retain options are specified always update the repo.
+    if (old_metadata_location && cr_repomd_compare(repomd_obj, old_metadata_location->repomd_data) &&
+        !cmd_options->retain_old && !cmd_options->retain_old_md_by_age) {
+        g_message("New and old repodata match, not updating.");
+        if (cr_rm(tmp_out_repo, CR_RM_RECURSIVE, NULL, &tmp_err)) {
+            g_debug("tmp_out_repo %s removed", tmp_out_repo);
+        } else {
+            g_warning("Cannot remove %s: %s", tmp_out_repo, tmp_err->message);
+            g_clear_error(&tmp_err);
+        }
+
+        goto cleanup;
+    }
+
     char *repomd_xml = cr_xml_dump_repomd(repomd_obj, &tmp_err);
     assert(repomd_xml || tmp_err);
-    cr_repomd_free(repomd_obj);
 
     if (!repomd_xml) {
         g_critical("Cannot generate repomd.xml: %s", tmp_err->message);
@@ -2061,14 +2074,6 @@ deltaerror:
         g_debug("Renamed %s -> %s", tmp_out_repo, out_repo);
     }
 
-    // Remove lock
-    if (g_strcmp0(lock_dir, tmp_out_repo))
-        // If lock_dir is not same as temporary repo dir then remove it
-        cr_remove_dir(lock_dir, NULL);
-
-    // Disable path stored for exit handler
-    cr_unset_cleanup_handler(NULL);
-
     sigprocmask(SIG_SETMASK, &old_mask, NULL);
 
     // === End of section that has to be maximally atomic ===
@@ -2084,15 +2089,29 @@ deltaerror:
     }
 
 
+    g_free(old_repodata_path);
+
+cleanup:
     // Clean up
     g_debug("Memory cleanup");
 
+    cr_repomd_free(repomd_obj);
+
+    // Remove lock
+    if (g_strcmp0(lock_dir, tmp_out_repo))
+        // If lock_dir is not same as temporary repo dir then remove it
+        cr_remove_dir(lock_dir, NULL);
+
+    // Disable path stored for exit handler
+    cr_unset_cleanup_handler(NULL);
+
+    cr_metadatalocation_free(old_metadata_location);
+
     if (old_metadata)
         cr_metadata_free(old_metadata);
 
     g_free(user_data.prev_srpm);
     g_free(user_data.cur_srpm);
-    g_free(old_repodata_path);
     g_free(in_repo);
     g_free(out_repo);
     g_free(tmp_out_repo);