Don't permit the same commit twice on the same change

Repeated uses of "repo upload --replace" for the same change id
and commit, without changing the commit SHA-1, would create more
than one patch set with identical content.  This is confusing to
read and review.  Disallowing it simplifies things for any reader.

Caused-by: jbq
Signed-off-by: Shawn O. Pearce <sop@google.com>

2 files changed, 13 insertions, 0 deletions

diff --git a/appjar/src/main/java/com/google/gerrit/client/reviewdb/PatchSetAccess.java b/appjar/src/main/java/com/google/gerrit/client/reviewdb/PatchSetAccess.java
index 811b60a1f0..2819b873b1 100644
--- a/appjar/src/main/java/com/google/gerrit/client/reviewdb/PatchSetAccess.java
+++ b/appjar/src/main/java/com/google/gerrit/client/reviewdb/PatchSetAccess.java
@@ -27,6 +27,10 @@ public interface PatchSetAccess extends Access<PatchSet, PatchSet.Id> {
   @Query("WHERE id.changeId = ? ORDER BY id.patchSetId")
   ResultSet<PatchSet> byChange(Change.Id id) throws OrmException;
 
+  @Query("WHERE id.changeId = ? AND revision = ?")
+  ResultSet<PatchSet> byChangeRevision(Change.Id id, RevId rev)
+      throws OrmException;
+
   @Query("WHERE revision = ? LIMIT 2")
   ResultSet<PatchSet> byRevision(RevId rev) throws OrmException;
 
diff --git a/appjar/src/main/java/com/google/gerrit/server/ssh/Receive.java b/appjar/src/main/java/com/google/gerrit/server/ssh/Receive.java
index 1706a0c6ce..2798fccf2c 100644
--- a/appjar/src/main/java/com/google/gerrit/server/ssh/Receive.java
+++ b/appjar/src/main/java/com/google/gerrit/server/ssh/Receive.java
@@ -28,6 +28,7 @@ import com.google.gerrit.client.reviewdb.ChangeMessage;
 import com.google.gerrit.client.reviewdb.ContactInformation;
 import com.google.gerrit.client.reviewdb.ContributorAgreement;
 import com.google.gerrit.client.reviewdb.PatchSet;
+import com.google.gerrit.client.reviewdb.RevId;
 import com.google.gerrit.client.reviewdb.ReviewDb;
 import com.google.gerrit.client.rpc.Common;
 import com.google.gerrit.git.PatchSetImporter;
@@ -597,6 +598,14 @@ class Receive extends AbstractGitCommand {
           change = changeCache.get(changeId);
         }
 
+        // Don't allow the same commit to appear twice on the same change
+        //
+        if (!db.patchSets().byChangeRevision(changeId,
+            new RevId(cmd.getNewId().name())).toList().isEmpty()) {
+          reject(cmd, "patch set exists");
+          return null;
+        }
+
         final PatchSet ps = new PatchSet(change.newPatchSetId());
         ps.setCreatedOn(new Timestamp(System.currentTimeMillis()));
         ps.setUploader(userAccount.getId());