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gerrit/gerrit/9919b3eb99426b411dbeedd53120f5e01d88e492^!/.
commit
9919b3eb99426b411dbeedd53120f5e01d88e492
[log]
author
Dave Borowitz <dborowitz@google.com>
Tue Apr 23 14:39:28 2019 -0700
committer
Dave Borowitz <dborowitz@google.com>
Mon Apr 29 07:42:11 2019 -0700
tree
3173235147903125eec706f0f7aa8ad0b33183aa
parent
20a984f7509c07caed42f56c3d588078e1c1971a [diff]
Add utility methods and constants for abbreviating ObjectIds

There are a variety of ways to abbreviate ObjectId hex strings: with an
arbitrary default length or an explicit length, with or without an
ObjectReader for final disambiguation. Cut down on the amount of
hard-coding and save a few characters by introducing a consistent set of
abbreviateName static methods.

This class is also a convenient place to put a constant for the default
abbreviation length (7), which doesn't exist in JGit (e.g. it's
hard-coded in ObjectReader.java). Since we have that constant, also add
another constant that copies Constants.OBJECT_ID_STRING_LENGTH. In
general we avoid duplicating JGit constants in Gerrit, but in this case
the upstream constant is quite verbose, and also it's cleaner at call
sites in Gerrit to be using two constants from ObjectIds with a
consistent naming pattern.

This change preserves existing abbreviation behavior in all cases.

Change-Id: I2b6a30c1ee122c6d0e149cd19b5e23a4ac4294da

diff --git a/java/com/google/gerrit/acceptance/BUILD b/java/com/google/gerrit/acceptance/BUILD
index ed0de9c..0714d22 100644
--- a/java/com/google/gerrit/acceptance/BUILD
+++ b/java/com/google/gerrit/acceptance/BUILD

@@ -14,6 +14,7 @@
         "//java/com/google/gerrit/extensions:api",
         "//java/com/google/gerrit/extensions/common/testing:common-test-util",
         "//java/com/google/gerrit/extensions/restapi/testing:restapi-test-util",
+        "//java/com/google/gerrit/git",
         "//java/com/google/gerrit/git/testing",
         "//java/com/google/gerrit/gpg/testing:gpg-test-util",
         "//java/com/google/gerrit/httpd",

diff --git a/java/com/google/gerrit/git/ObjectIds.java b/java/com/google/gerrit/git/ObjectIds.java
new file mode 100644
index 0000000..9a605d2
--- /dev/null
+++ b/java/com/google/gerrit/git/ObjectIds.java

@@ -0,0 +1,90 @@
+// Copyright (C) 2019 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.git;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static java.util.Objects.requireNonNull;
+
+import java.io.IOException;
+import org.eclipse.jgit.lib.AnyObjectId;
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.ObjectReader;
+
+/** Static utilities for working with {@code ObjectId}s. */
+public class ObjectIds {
+  /** Length of a hex SHA-1 string. */
+  public static final int STR_LEN = Constants.OBJECT_ID_STRING_LENGTH;
+
+  /** Default abbreviated length of a hex SHA-1 string. */
+  public static final int ABBREV_STR_LEN = 7;
+
+  /**
+   * Abbreviate an ID's hex string representation to 7 chars.
+   *
+   * @param id object ID.
+   * @return abbreviated hex string representation, exactly 7 chars.
+   */
+  public static String abbreviateName(AnyObjectId id) {
+    return abbreviateName(id, ABBREV_STR_LEN);
+  }
+
+  /**
+   * Abbreviate an ID's hex string representation to {@code n} chars.
+   *
+   * @param id object ID.
+   * @param n number of hex chars, 1 to 40.
+   * @return abbreviated hex string representation, exactly {@code n} chars.
+   */
+  public static String abbreviateName(AnyObjectId id, int n) {
+    checkValidLength(n);
+    return requireNonNull(id).abbreviate(n).name();
+  }
+
+  /**
+   * Abbreviate an ID's hex string representation uniquely to at least 7 chars.
+   *
+   * @param id object ID.
+   * @param reader object reader for determining uniqueness.
+   * @return abbreviated hex string representation, unique according to {@code reader} at least 7
+   *     chars.
+   * @throws IOException if an error occurs while looking for ambiguous objects.
+   */
+  public static String abbreviateName(AnyObjectId id, ObjectReader reader) throws IOException {
+    return abbreviateName(id, ABBREV_STR_LEN, reader);
+  }
+
+  /**
+   * Abbreviate an ID's hex string representation uniquely to at least {@code n} chars.
+   *
+   * @param id object ID.
+   * @param n minimum number of hex chars, 1 to 40.
+   * @param reader object reader for determining uniqueness.
+   * @return abbreviated hex string representation, unique according to {@code reader} at least
+   *     {@code n} chars.
+   * @throws IOException if an error occurs while looking for ambiguous objects.
+   */
+  public static String abbreviateName(AnyObjectId id, int n, ObjectReader reader)
+      throws IOException {
+    checkValidLength(n);
+    return reader.abbreviate(id, n).name();
+  }
+
+  private static void checkValidLength(int n) {
+    checkArgument(n > 0);
+    checkArgument(n <= STR_LEN);
+  }
+
+  private ObjectIds() {}
+}

diff --git a/java/com/google/gerrit/index/BUILD b/java/com/google/gerrit/index/BUILD
index dfdc014..7fcf342 100644
--- a/java/com/google/gerrit/index/BUILD
+++ b/java/com/google/gerrit/index/BUILD

@@ -22,6 +22,7 @@
         "//java/com/google/gerrit/common:annotations",
         "//java/com/google/gerrit/exceptions",
         "//java/com/google/gerrit/extensions:api",
+        "//java/com/google/gerrit/git",
         "//java/com/google/gerrit/json",
         "//java/com/google/gerrit/metrics",
         "//java/com/google/gerrit/reviewdb:server",

diff --git a/java/com/google/gerrit/index/RefState.java b/java/com/google/gerrit/index/RefState.java
index 8ffaa36..dd8bcfa 100644
--- a/java/com/google/gerrit/index/RefState.java
+++ b/java/com/google/gerrit/index/RefState.java

@@ -23,10 +23,10 @@
 import com.google.common.collect.MultimapBuilder;
 import com.google.common.collect.SetMultimap;
 import com.google.gerrit.common.Nullable;
+import com.google.gerrit.git.ObjectIds;
 import com.google.gerrit.reviewdb.client.Project;
 import java.io.IOException;
 import java.util.List;
-import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
@@ -61,7 +61,7 @@
 
   public byte[] toByteArray(Project.NameKey project) {
     byte[] a = (project.toString() + ':' + ref() + ':').getBytes(UTF_8);
-    byte[] b = new byte[a.length + Constants.OBJECT_ID_STRING_LENGTH];
+    byte[] b = new byte[a.length + ObjectIds.STR_LEN];
     System.arraycopy(a, 0, b, 0, a.length);
     id().copyTo(b, a.length);
     return b;

diff --git a/java/com/google/gerrit/reviewdb/client/RevId.java b/java/com/google/gerrit/reviewdb/client/RevId.java
index cfcd9d9..de72154 100644
--- a/java/com/google/gerrit/reviewdb/client/RevId.java
+++ b/java/com/google/gerrit/reviewdb/client/RevId.java

@@ -16,8 +16,6 @@
 
 /** A revision identifier for a file or a change. */
 public final class RevId {
-  public static final int ABBREV_LEN = 7;
-  public static final int LEN = 40;
 
   protected String id;
 

diff --git a/java/com/google/gerrit/server/account/externalids/ExternalId.java b/java/com/google/gerrit/server/account/externalids/ExternalId.java
index dc80904..6583a7e 100644
--- a/java/com/google/gerrit/server/account/externalids/ExternalId.java
+++ b/java/com/google/gerrit/server/account/externalids/ExternalId.java

@@ -27,6 +27,7 @@
 import com.google.common.hash.Hashing;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.extensions.client.AuthType;
+import com.google.gerrit.git.ObjectIds;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.server.account.HashedPassword;
 import java.io.Serializable;
@@ -38,7 +39,6 @@
 import java.util.stream.Stream;
 import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.lib.Config;
-import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 
 @AutoValue
@@ -428,10 +428,10 @@
 
   public byte[] toByteArray() {
     checkState(blobId() != null, "Missing blobId in external ID %s", key().get());
-    byte[] b = new byte[2 * Constants.OBJECT_ID_STRING_LENGTH + 1];
+    byte[] b = new byte[2 * ObjectIds.STR_LEN + 1];
     key().sha1().copyTo(b, 0);
-    b[Constants.OBJECT_ID_STRING_LENGTH] = ':';
-    blobId().copyTo(b, Constants.OBJECT_ID_STRING_LENGTH + 1);
+    b[ObjectIds.STR_LEN] = ':';
+    blobId().copyTo(b, ObjectIds.STR_LEN + 1);
     return b;
   }
 

diff --git a/java/com/google/gerrit/server/change/ChangeFinder.java b/java/com/google/gerrit/server/change/ChangeFinder.java
index 6f81ad6..0535a4e 100644
--- a/java/com/google/gerrit/server/change/ChangeFinder.java
+++ b/java/com/google/gerrit/server/change/ChangeFinder.java

@@ -23,6 +23,7 @@
 import com.google.gerrit.exceptions.StorageException;
 import com.google.gerrit.extensions.restapi.DeprecatedIdentifierException;
 import com.google.gerrit.extensions.restapi.Url;
+import com.google.gerrit.git.ObjectIds;
 import com.google.gerrit.index.IndexConfig;
 import com.google.gerrit.metrics.Counter1;
 import com.google.gerrit.metrics.Description;
@@ -30,7 +31,6 @@
 import com.google.gerrit.metrics.MetricMaker;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.Project;
-import com.google.gerrit.reviewdb.client.RevId;
 import com.google.gerrit.server.cache.CacheModule;
 import com.google.gerrit.server.config.ConfigUtil;
 import com.google.gerrit.server.config.GerritServerConfig;
@@ -169,7 +169,7 @@
     InternalChangeQuery query = queryProvider.get().noFields();
 
     // Try commit hash
-    if (id.matches("^([0-9a-fA-F]{" + RevId.ABBREV_LEN + "," + RevId.LEN + "})$")) {
+    if (id.matches("^([0-9a-fA-F]{" + ObjectIds.ABBREV_STR_LEN + "," + ObjectIds.STR_LEN + "})$")) {
       checkIdType(ChangeIdType.COMMIT_HASH, enforceDeprecation, id);
       return asChangeNotes(query.byCommit(id));
     }

diff --git a/java/com/google/gerrit/server/git/MergeUtil.java b/java/com/google/gerrit/server/git/MergeUtil.java
index 5322daa..05bcfb7 100644
--- a/java/com/google/gerrit/server/git/MergeUtil.java
+++ b/java/com/google/gerrit/server/git/MergeUtil.java

@@ -17,6 +17,7 @@
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkState;
 import static com.google.common.collect.ImmutableSet.toImmutableSet;
+import static com.google.gerrit.git.ObjectIds.abbreviateName;
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static java.util.Objects.requireNonNull;
 
@@ -337,13 +338,13 @@
         String.format(
             "%0$-" + nameLength + "s (%s %s)",
             oursName,
-            ours.abbreviate(6).name(),
+            abbreviateName(ours, 6),
             oursMsg.substring(0, Math.min(oursMsg.length(), 60)));
     String theirsNameFormatted =
         String.format(
             "%0$-" + nameLength + "s (%s %s)",
             theirsName,
-            theirs.abbreviate(6).name(),
+            abbreviateName(theirs, 6),
             theirsMsg.substring(0, Math.min(theirsMsg.length(), 60)));
 
     MergeFormatter fmt = new MergeFormatter();

diff --git a/java/com/google/gerrit/server/git/receive/BUILD b/java/com/google/gerrit/server/git/receive/BUILD
index da21fbb..a4f4d93 100644
--- a/java/com/google/gerrit/server/git/receive/BUILD
+++ b/java/com/google/gerrit/server/git/receive/BUILD

@@ -7,6 +7,7 @@
         "//java/com/google/gerrit/common:server",
         "//java/com/google/gerrit/exceptions",
         "//java/com/google/gerrit/extensions:api",
+        "//java/com/google/gerrit/git",
         "//java/com/google/gerrit/metrics",
         "//java/com/google/gerrit/reviewdb:server",
         "//java/com/google/gerrit/server",

diff --git a/java/com/google/gerrit/server/git/receive/BranchCommitValidator.java b/java/com/google/gerrit/server/git/receive/BranchCommitValidator.java
index 2d1d1a9..d3081f4 100644
--- a/java/com/google/gerrit/server/git/receive/BranchCommitValidator.java
+++ b/java/com/google/gerrit/server/git/receive/BranchCommitValidator.java

@@ -14,6 +14,7 @@
 
 package com.google.gerrit.server.git.receive;
 
+import static com.google.gerrit.git.ObjectIds.abbreviateName;
 import static org.eclipse.jgit.transport.ReceiveCommand.Result.REJECTED_OTHER_REASON;
 
 import com.google.common.flogger.FluentLogger;
@@ -21,7 +22,6 @@
 import com.google.gerrit.reviewdb.client.BranchNameKey;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.Project;
-import com.google.gerrit.reviewdb.client.RevId;
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.events.CommitReceivedEvent;
 import com.google.gerrit.server.git.validators.CommitValidationException;
@@ -127,6 +127,6 @@
   }
 
   private String messageForCommit(RevCommit c, String msg) {
-    return String.format("commit %s: %s", c.abbreviate(RevId.ABBREV_LEN).name(), msg);
+    return String.format("commit %s: %s", abbreviateName(c), msg);
   }
 }

diff --git a/java/com/google/gerrit/server/git/receive/HackPushNegotiateHook.java b/java/com/google/gerrit/server/git/receive/HackPushNegotiateHook.java
index 9bad21d..251a799 100644
--- a/java/com/google/gerrit/server/git/receive/HackPushNegotiateHook.java
+++ b/java/com/google/gerrit/server/git/receive/HackPushNegotiateHook.java

@@ -18,12 +18,12 @@
 
 import com.google.common.collect.Sets;
 import com.google.common.flogger.FluentLogger;
+import com.google.gerrit.git.ObjectIds;
 import java.io.IOException;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Map;
 import java.util.Set;
-import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.revwalk.RevCommit;
@@ -49,7 +49,7 @@
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
   /** Size of an additional ".have" line. */
-  private static final int HAVE_LINE_LEN = 4 + Constants.OBJECT_ID_STRING_LENGTH + 1 + 5 + 1;
+  private static final int HAVE_LINE_LEN = 4 + ObjectIds.STR_LEN + 1 + 5 + 1;
 
   /**
    * Maximum number of bytes to "waste" in the advertisement with a peek at this repository's

diff --git a/java/com/google/gerrit/server/git/receive/ReceiveCommits.java b/java/com/google/gerrit/server/git/receive/ReceiveCommits.java
index d060a1e..60fc0a9 100644
--- a/java/com/google/gerrit/server/git/receive/ReceiveCommits.java
+++ b/java/com/google/gerrit/server/git/receive/ReceiveCommits.java

@@ -20,6 +20,7 @@
 import static com.google.common.collect.ImmutableSet.toImmutableSet;
 import static com.google.common.flogger.LazyArgs.lazy;
 import static com.google.gerrit.common.FooterConstants.CHANGE_ID;
+import static com.google.gerrit.git.ObjectIds.abbreviateName;
 import static com.google.gerrit.reviewdb.client.RefNames.REFS_CHANGES;
 import static com.google.gerrit.reviewdb.client.RefNames.isConfigRef;
 import static com.google.gerrit.server.change.HashtagsUtil.cleanupHashtag;
@@ -2349,7 +2350,7 @@
             rw.parseBody(c);
             messages.add(
                 new CommitValidationMessage(
-                    "Implicit Merge of " + c.abbreviate(7).name() + " " + c.getShortMessage(),
+                    "Implicit Merge of " + abbreviateName(c) + " " + c.getShortMessage(),
                     ValidationMessage.Type.ERROR));
           }
           reject(magicBranch.cmd, "implicit merges detected");
@@ -2778,10 +2779,10 @@
           addMessage(
               String.format(
                   "warning: no changes between prior commit %s and new commit %s",
-                  reader.abbreviate(priorCommit).name(), reader.abbreviate(newCommit).name()));
+                  abbreviateName(priorCommit, reader), abbreviateName(newCommit, reader)));
         } else {
           StringBuilder msg = new StringBuilder();
-          msg.append("warning: ").append(reader.abbreviate(newCommit).name());
+          msg.append("warning: ").append(abbreviateName(newCommit, reader));
           msg.append(":");
           msg.append(" no files changed");
           if (!authorEq) {

diff --git a/java/com/google/gerrit/server/index/group/GroupField.java b/java/com/google/gerrit/server/index/group/GroupField.java
index 29e3867..83c1625 100644
--- a/java/com/google/gerrit/server/index/group/GroupField.java
+++ b/java/com/google/gerrit/server/index/group/GroupField.java

@@ -23,13 +23,13 @@
 import static com.google.gerrit.index.FieldDef.timestamp;
 
 import com.google.common.base.MoreObjects;
+import com.google.gerrit.git.ObjectIds;
 import com.google.gerrit.index.FieldDef;
 import com.google.gerrit.index.SchemaUtil;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.AccountGroup;
 import com.google.gerrit.server.group.InternalGroup;
 import java.sql.Timestamp;
-import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 
 /** Secondary index schemas for groups. */
@@ -82,7 +82,7 @@
       storedOnly("ref_state")
           .build(
               g -> {
-                byte[] a = new byte[Constants.OBJECT_ID_STRING_LENGTH];
+                byte[] a = new byte[ObjectIds.STR_LEN];
                 MoreObjects.firstNonNull(g.getRefState(), ObjectId.zeroId()).copyTo(a, 0);
                 return a;
               });

diff --git a/java/com/google/gerrit/server/patch/Text.java b/java/com/google/gerrit/server/patch/Text.java
index 172dbaf..f127f44 100644
--- a/java/com/google/gerrit/server/patch/Text.java
+++ b/java/com/google/gerrit/server/patch/Text.java

@@ -18,6 +18,7 @@
 import static java.nio.charset.StandardCharsets.UTF_8;
 
 import com.google.common.flogger.FluentLogger;
+import com.google.gerrit.git.ObjectIds;
 import java.io.IOException;
 import java.nio.charset.Charset;
 import java.nio.charset.IllegalCharsetNameException;
@@ -62,7 +63,7 @@
             RevCommit p = c.getParent(0);
             rw.parseBody(p);
             b.append("Parent:     ");
-            b.append(reader.abbreviate(p, 8).name());
+            b.append(abbreviateName(p, reader));
             b.append(" (");
             b.append(p.getShortMessage());
             b.append(")\n");
@@ -73,7 +74,7 @@
             RevCommit p = c.getParent(i);
             rw.parseBody(p);
             b.append(i == 0 ? "Merge Of:   " : "            ");
-            b.append(reader.abbreviate(p, 8).name());
+            b.append(abbreviateName(p, reader));
             b.append(" (");
             b.append(p.getShortMessage());
             b.append(")\n");
@@ -106,7 +107,7 @@
           b.append("Merge List:\n\n");
           for (RevCommit commit : MergeListBuilder.build(rw, c, uniterestingParent)) {
             b.append("* ");
-            b.append(reader.abbreviate(commit, 8).name());
+            b.append(abbreviateName(commit, reader));
             b.append(" ");
             b.append(commit.getShortMessage());
             b.append("\n");
@@ -116,6 +117,10 @@
     }
   }
 
+  private static String abbreviateName(RevCommit p, ObjectReader reader) throws IOException {
+    return ObjectIds.abbreviateName(p, 8, reader);
+  }
+
   private static void appendPersonIdent(StringBuilder b, String field, PersonIdent person) {
     if (person != null) {
       b.append(field).append(":    ");

diff --git a/java/com/google/gerrit/server/query/change/CommitPredicate.java b/java/com/google/gerrit/server/query/change/CommitPredicate.java
index 567f58d..a03193c 100644
--- a/java/com/google/gerrit/server/query/change/CommitPredicate.java
+++ b/java/com/google/gerrit/server/query/change/CommitPredicate.java

@@ -16,14 +16,14 @@
 
 import static com.google.gerrit.server.index.change.ChangeField.COMMIT;
 import static com.google.gerrit.server.index.change.ChangeField.EXACT_COMMIT;
-import static org.eclipse.jgit.lib.Constants.OBJECT_ID_STRING_LENGTH;
 
+import com.google.gerrit.git.ObjectIds;
 import com.google.gerrit.index.FieldDef;
 import com.google.gerrit.reviewdb.client.PatchSet;
 
 public class CommitPredicate extends ChangeIndexPredicate {
   static FieldDef<ChangeData, ?> commitField(String id) {
-    if (id.length() == OBJECT_ID_STRING_LENGTH) {
+    if (id.length() == ObjectIds.STR_LEN) {
       return EXACT_COMMIT;
     }
     return COMMIT;

diff --git a/java/com/google/gerrit/server/restapi/BUILD b/java/com/google/gerrit/server/restapi/BUILD
index 3040644..1eba9b3 100644
--- a/java/com/google/gerrit/server/restapi/BUILD
+++ b/java/com/google/gerrit/server/restapi/BUILD

@@ -10,6 +10,7 @@
         "//java/com/google/gerrit/common:server",
         "//java/com/google/gerrit/exceptions",
         "//java/com/google/gerrit/extensions:api",
+        "//java/com/google/gerrit/git",
         "//java/com/google/gerrit/index",
         "//java/com/google/gerrit/index:query_exception",
         "//java/com/google/gerrit/index/project",

diff --git a/java/com/google/gerrit/server/restapi/change/GetArchive.java b/java/com/google/gerrit/server/restapi/change/GetArchive.java
index 1bd1bce..b1f3645 100644
--- a/java/com/google/gerrit/server/restapi/change/GetArchive.java
+++ b/java/com/google/gerrit/server/restapi/change/GetArchive.java

@@ -14,6 +14,8 @@
 
 package com.google.gerrit.server.restapi.change;
 
+import static com.google.gerrit.git.ObjectIds.abbreviateName;
+
 import com.google.common.base.Strings;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.BinaryResult;
@@ -104,6 +106,6 @@
   private static String name(ArchiveFormat format, RevWalk rw, RevCommit commit)
       throws IOException {
     return String.format(
-        "%s%s", rw.getObjectReader().abbreviate(commit, 7).name(), format.getDefaultSuffix());
+        "%s%s", abbreviateName(commit, rw.getObjectReader()), format.getDefaultSuffix());
   }
 }

diff --git a/java/com/google/gerrit/server/restapi/change/GetPatch.java b/java/com/google/gerrit/server/restapi/change/GetPatch.java
index ccad9e0..e0c2ce9 100644
--- a/java/com/google/gerrit/server/restapi/change/GetPatch.java
+++ b/java/com/google/gerrit/server/restapi/change/GetPatch.java

@@ -14,6 +14,7 @@
 
 package com.google.gerrit.server.restapi.change;
 
+import static com.google.gerrit.git.ObjectIds.abbreviateName;
 import static java.nio.charset.StandardCharsets.UTF_8;
 
 import com.google.gerrit.extensions.restapi.BinaryResult;
@@ -31,7 +32,6 @@
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipOutputStream;
 import org.eclipse.jgit.diff.DiffFormatter;
-import org.eclipse.jgit.lib.AbbreviatedObjectId;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.PersonIdent;
 import org.eclipse.jgit.lib.Repository;
@@ -189,7 +189,6 @@
   }
 
   private static String fileName(RevWalk rw, RevCommit commit) throws IOException {
-    AbbreviatedObjectId id = rw.getObjectReader().abbreviate(commit, 7);
-    return id.name() + ".diff";
+    return abbreviateName(commit, rw.getObjectReader()) + ".diff";
   }
 }

diff --git a/java/com/google/gerrit/server/restapi/change/Revisions.java b/java/com/google/gerrit/server/restapi/change/Revisions.java
index b5fcba2..41c1a96 100644
--- a/java/com/google/gerrit/server/restapi/change/Revisions.java
+++ b/java/com/google/gerrit/server/restapi/change/Revisions.java

@@ -22,6 +22,7 @@
 import com.google.gerrit.extensions.restapi.IdString;
 import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
 import com.google.gerrit.extensions.restapi.RestView;
+import com.google.gerrit.git.ObjectIds;
 import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.reviewdb.client.RevId;
 import com.google.gerrit.server.PatchSetUtil;
@@ -121,7 +122,7 @@
     } else if (id.length() < 6 && id.matches("^[1-9][0-9]{0,4}$")) {
       // Legacy patch set number syntax.
       return byLegacyPatchSetId(change, id);
-    } else if (id.length() < 4 || id.length() > RevId.LEN) {
+    } else if (id.length() < 4 || id.length() > ObjectIds.STR_LEN) {
       // Require a minimum of 4 digits.
       // Impossibly long identifier will never match.
       return Collections.emptyList();
@@ -133,7 +134,7 @@
         }
       }
       // Not an existing patch set on a change, but might be an edit.
-      if (out.isEmpty() && id.length() == RevId.LEN) {
+      if (out.isEmpty() && id.length() == ObjectIds.STR_LEN) {
         return loadEdit(change, new RevId(id));
       }
       return out;

diff --git a/java/com/google/gerrit/server/restapi/change/Submit.java b/java/com/google/gerrit/server/restapi/change/Submit.java
index 73df1e7..73f61d1 100644
--- a/java/com/google/gerrit/server/restapi/change/Submit.java
+++ b/java/com/google/gerrit/server/restapi/change/Submit.java

@@ -14,6 +14,7 @@
 
 package com.google.gerrit.server.restapi.change;
 
+import static com.google.gerrit.git.ObjectIds.abbreviateName;
 import static java.util.stream.Collectors.joining;
 
 import com.google.common.base.MoreObjects;
@@ -369,7 +370,7 @@
         ImmutableMap.of(
             "patchSet", String.valueOf(resource.getPatchSet().getPatchSetId()),
             "branch", change.getDest().shortName(),
-            "commit", ObjectId.fromString(revId.get()).abbreviate(7).name(),
+            "commit", abbreviateName(ObjectId.fromString(revId.get())),
             "submitSize", String.valueOf(cs.size()));
     ParameterizedString tp = cs.size() > 1 ? titlePatternWithAncestors : titlePattern;
     return new UiAction.Description()

diff --git a/java/com/google/gerrit/sshd/BUILD b/java/com/google/gerrit/sshd/BUILD
index 42ef7d5..3a69554 100644
--- a/java/com/google/gerrit/sshd/BUILD
+++ b/java/com/google/gerrit/sshd/BUILD

@@ -7,6 +7,7 @@
         "//java/com/google/gerrit/common:server",
         "//java/com/google/gerrit/exceptions",
         "//java/com/google/gerrit/extensions:api",
+        "//java/com/google/gerrit/git",
         "//java/com/google/gerrit/json",
         "//java/com/google/gerrit/lifecycle",
         "//java/com/google/gerrit/lucene",

diff --git a/java/com/google/gerrit/sshd/commands/PatchSetParser.java b/java/com/google/gerrit/sshd/commands/PatchSetParser.java
index 7cee37f..5296f1d 100644
--- a/java/com/google/gerrit/sshd/commands/PatchSetParser.java
+++ b/java/com/google/gerrit/sshd/commands/PatchSetParser.java

@@ -15,10 +15,10 @@
 package com.google.gerrit.sshd.commands;
 
 import com.google.gerrit.common.Nullable;
+import com.google.gerrit.git.ObjectIds;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.reviewdb.client.Project;
-import com.google.gerrit.reviewdb.client.RevId;
 import com.google.gerrit.server.PatchSetUtil;
 import com.google.gerrit.server.change.ChangeFinder;
 import com.google.gerrit.server.notedb.ChangeNotes;
@@ -56,7 +56,7 @@
       throws UnloggedFailure {
     // By commit?
     //
-    if (token.matches("^([0-9a-fA-F]{4," + RevId.LEN + "})$")) {
+    if (token.matches("^([0-9a-fA-F]{4," + ObjectIds.STR_LEN + "})$")) {
       InternalChangeQuery query = queryProvider.get();
       List<ChangeData> cds;
       if (projectState != null) {

diff --git a/java/com/google/gerrit/sshd/commands/Receive.java b/java/com/google/gerrit/sshd/commands/Receive.java
index fa0e37b..40404f1 100644
--- a/java/com/google/gerrit/sshd/commands/Receive.java
+++ b/java/com/google/gerrit/sshd/commands/Receive.java

@@ -14,6 +14,8 @@
 
 package com.google.gerrit.sshd.commands;
 
+import static com.google.gerrit.git.ObjectIds.abbreviateName;
+
 import com.google.common.collect.MultimapBuilder;
 import com.google.common.collect.SetMultimap;
 import com.google.common.flogger.FluentLogger;
@@ -141,7 +143,7 @@
         msg.append("  Visible references (").append(adv.size()).append("):\n");
         for (Ref ref : adv.values()) {
           msg.append("  - ")
-              .append(ref.getObjectId().abbreviate(8).name())
+              .append(abbreviateName(ref.getObjectId(), 8))
               .append(" ")
               .append(ref.getName())
               .append("\n");
@@ -158,7 +160,7 @@
         msg.append("  Hidden references (").append(hidden.size()).append("):\n");
         for (Ref ref : hidden) {
           msg.append("  - ")
-              .append(ref.getObjectId().abbreviate(8).name())
+              .append(abbreviateName(ref.getObjectId(), 8))
               .append(" ")
               .append(ref.getName())
               .append("\n");

diff --git a/javatests/com/google/gerrit/acceptance/api/change/MergeListIT.java b/javatests/com/google/gerrit/acceptance/api/change/MergeListIT.java
index a08d417..1b65e92 100644
--- a/javatests/com/google/gerrit/acceptance/api/change/MergeListIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/change/MergeListIT.java

@@ -15,6 +15,7 @@
 package com.google.gerrit.acceptance.api.change;
 
 import static com.google.common.truth.Truth.assertThat;
+import static com.google.gerrit.git.ObjectIds.abbreviateName;
 import static com.google.gerrit.reviewdb.client.Patch.MERGE_LIST;
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.eclipse.jgit.lib.Constants.HEAD;
@@ -171,7 +172,7 @@
     for (RevCommit c : commits) {
       mergeList
           .append("* ")
-          .append(c.abbreviate(8).name())
+          .append(abbreviateName(c, 8))
           .append(" ")
           .append(c.getShortMessage())
           .append("\n");

diff --git a/javatests/com/google/gerrit/acceptance/api/revision/RevisionDiffIT.java b/javatests/com/google/gerrit/acceptance/api/revision/RevisionDiffIT.java
index cbfc09f..a8a19ac 100644
--- a/javatests/com/google/gerrit/acceptance/api/revision/RevisionDiffIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/revision/RevisionDiffIT.java

@@ -18,6 +18,7 @@
 import static com.google.common.truth.TruthJUnit.assume;
 import static com.google.gerrit.extensions.common.testing.DiffInfoSubject.assertThat;
 import static com.google.gerrit.extensions.common.testing.FileInfoSubject.assertThat;
+import static com.google.gerrit.git.ObjectIds.abbreviateName;
 import static com.google.gerrit.reviewdb.client.Patch.COMMIT_MSG;
 import static java.util.stream.Collectors.joining;
 import static java.util.stream.Collectors.toMap;
@@ -2481,7 +2482,7 @@
 
       RevCommit parentCommit = c.getParents()[0];
       String parentCommitId =
-          testRepo.getRevWalk().getObjectReader().abbreviate(parentCommit.getId(), 8).name();
+          abbreviateName(parentCommit, 8, testRepo.getRevWalk().getObjectReader());
       headers.add("Parent:     " + parentCommitId + " (" + parentCommit.getShortMessage() + ")");
 
       SimpleDateFormat dtfmt = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z", Locale.US);

diff --git a/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java b/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java
index f58294b..a569cfa 100644
--- a/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java

@@ -23,6 +23,7 @@
 import static com.google.gerrit.acceptance.PushOneCommit.SUBJECT;
 import static com.google.gerrit.extensions.client.ListChangesOption.ALL_REVISIONS;
 import static com.google.gerrit.extensions.client.ListChangesOption.DETAILED_LABELS;
+import static com.google.gerrit.git.ObjectIds.abbreviateName;
 import static com.google.gerrit.reviewdb.client.Patch.COMMIT_MSG;
 import static com.google.gerrit.reviewdb.client.Patch.MERGE_LIST;
 import static com.google.gerrit.server.group.SystemGroupBackend.REGISTERED_USERS;
@@ -549,8 +550,8 @@
     ByteArrayOutputStream os = new ByteArrayOutputStream();
     bin.writeTo(os);
     String fileContent = new String(os.toByteArray(), UTF_8);
-    String destSha1 = getRemoteHead(project, destBranch).abbreviate(6).name();
-    String changeSha1 = r.getCommit().abbreviate(6).name();
+    String destSha1 = abbreviateName(getRemoteHead(project, destBranch), 6);
+    String changeSha1 = abbreviateName(r.getCommit(), 6);
     assertThat(fileContent)
         .isEqualTo(
             "<<<<<<< HEAD   ("

diff --git a/javatests/com/google/gerrit/acceptance/git/AbstractPushForReview.java b/javatests/com/google/gerrit/acceptance/git/AbstractPushForReview.java
index db18158..dcd1246 100644
--- a/javatests/com/google/gerrit/acceptance/git/AbstractPushForReview.java
+++ b/javatests/com/google/gerrit/acceptance/git/AbstractPushForReview.java

@@ -31,6 +31,7 @@
 import static com.google.gerrit.extensions.client.ListChangesOption.DETAILED_LABELS;
 import static com.google.gerrit.extensions.client.ListChangesOption.MESSAGES;
 import static com.google.gerrit.extensions.common.testing.EditInfoSubject.assertThat;
+import static com.google.gerrit.git.ObjectIds.abbreviateName;
 import static com.google.gerrit.server.git.receive.ReceiveConstants.PUSH_OPTION_SKIP_VALIDATION;
 import static com.google.gerrit.server.group.SystemGroupBackend.ANONYMOUS_USERS;
 import static com.google.gerrit.server.group.SystemGroupBackend.REGISTERED_USERS;
@@ -87,7 +88,6 @@
 import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.gerrit.reviewdb.client.RefNames;
-import com.google.gerrit.reviewdb.client.RevId;
 import com.google.gerrit.server.ChangeMessagesUtil;
 import com.google.gerrit.server.git.receive.NoteDbPushOption;
 import com.google.gerrit.server.git.receive.ReceiveConstants;
@@ -1592,8 +1592,7 @@
     RemoteRefUpdate refUpdate = r.getRemoteUpdate(ref);
     assertThat(refUpdate.getStatus()).isEqualTo(RemoteRefUpdate.Status.REJECTED_OTHER_REASON);
     String reason =
-        String.format(
-            "commit %s: missing Change-Id in message footer", c.toObjectId().abbreviate(7).name());
+        String.format("commit %s: missing Change-Id in message footer", abbreviateName(c));
     assertThat(refUpdate.getMessage()).isEqualTo(reason);
 
     assertThat(r.getMessages()).contains("\nERROR: " + reason);
@@ -1618,8 +1617,7 @@
     r.assertErrorStatus(
         String.format(
             "commit %s: %s",
-            r.getCommit().abbreviate(RevId.ABBREV_LEN).name(),
-            ChangeIdValidator.CHANGE_ID_MISMATCH_MSG));
+            abbreviateName(r.getCommit()), ChangeIdValidator.CHANGE_ID_MISMATCH_MSG));
   }
 
   @Test
@@ -2352,9 +2350,9 @@
     assertThat(pr.getMessages())
         .contains(
             "warning: no changes between prior commit "
-                + c.abbreviate(7).name()
+                + abbreviateName(c)
                 + " and new commit "
-                + amended.abbreviate(7).name());
+                + abbreviateName(amended));
   }
 
   @Test
@@ -2380,8 +2378,7 @@
     pr = pushHead(testRepo, r, false);
     assertPushOk(pr, r);
     assertThat(pr.getMessages())
-        .contains(
-            "warning: " + amended.abbreviate(7).name() + ": no files changed, message updated");
+        .contains("warning: " + abbreviateName(amended) + ": no files changed, message updated");
   }
 
   @Test
@@ -2405,8 +2402,7 @@
     pr = pushHead(testRepo, r, false);
     assertPushOk(pr, r);
     assertThat(pr.getMessages())
-        .contains(
-            "warning: " + amended.abbreviate(7).name() + ": no files changed, author changed");
+        .contains("warning: " + abbreviateName(amended) + ": no files changed, author changed");
   }
 
   @Test
@@ -2433,7 +2429,7 @@
     pr = pushHead(testRepo, r, false);
     assertPushOk(pr, r);
     assertThat(pr.getMessages())
-        .contains("warning: " + amended.abbreviate(7).name() + ": no files changed, was rebased");
+        .contains("warning: " + abbreviateName(amended) + ": no files changed, was rebased");
   }
 
   @Test

diff --git a/javatests/com/google/gerrit/acceptance/git/BUILD b/javatests/com/google/gerrit/acceptance/git/BUILD
index 0c43d8c..e4a643c 100644
--- a/javatests/com/google/gerrit/acceptance/git/BUILD
+++ b/javatests/com/google/gerrit/acceptance/git/BUILD

@@ -7,6 +7,7 @@
     deps = [
         ":push_for_review",
         ":submodule_util",
+        "//java/com/google/gerrit/git",
         "//lib/commons:lang",
     ],
 )
@@ -17,6 +18,7 @@
     srcs = ["AbstractPushForReview.java"],
     deps = [
         "//java/com/google/gerrit/acceptance:lib",
+        "//java/com/google/gerrit/git",
         "//java/com/google/gerrit/mail",
     ],
 )

diff --git a/javatests/com/google/gerrit/acceptance/git/ImplicitMergeCheckIT.java b/javatests/com/google/gerrit/acceptance/git/ImplicitMergeCheckIT.java
index 6516b32..7beae98 100644
--- a/javatests/com/google/gerrit/acceptance/git/ImplicitMergeCheckIT.java
+++ b/javatests/com/google/gerrit/acceptance/git/ImplicitMergeCheckIT.java

@@ -16,6 +16,7 @@
 
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.gerrit.acceptance.GitUtil.pushHead;
+import static com.google.gerrit.git.ObjectIds.abbreviateName;
 
 import com.google.gerrit.acceptance.AbstractDaemonTest;
 import com.google.gerrit.acceptance.PushOneCommit;
@@ -77,7 +78,7 @@
   }
 
   private static String implicitMergeOf(ObjectId commit) {
-    return "implicit merge of " + commit.abbreviate(7).name();
+    return "implicit merge of " + abbreviateName(commit);
   }
 
   private void setRejectImplicitMerges() throws Exception {

diff --git a/javatests/com/google/gerrit/acceptance/ssh/UploadArchiveIT.java b/javatests/com/google/gerrit/acceptance/ssh/UploadArchiveIT.java
index 03b7143..6e4c8b2 100644
--- a/javatests/com/google/gerrit/acceptance/ssh/UploadArchiveIT.java
+++ b/javatests/com/google/gerrit/acceptance/ssh/UploadArchiveIT.java

@@ -15,6 +15,7 @@
 package com.google.gerrit.acceptance.ssh;
 
 import static com.google.common.truth.Truth.assertThat;
+import static com.google.gerrit.git.ObjectIds.abbreviateName;
 
 import com.google.common.base.Splitter;
 import com.google.gerrit.acceptance.AbstractDaemonTest;
@@ -55,7 +56,7 @@
   @Test
   public void zipFormat() throws Exception {
     PushOneCommit.Result r = createChange();
-    String abbreviated = r.getCommit().abbreviate(8).name();
+    String abbreviated = abbreviateName(r.getCommit(), 8);
     String c = command(r, "zip", abbreviated);
 
     InputStream out =
@@ -92,7 +93,7 @@
   @Test
   public void txzFormat() throws Exception {
     PushOneCommit.Result r = createChange();
-    String abbreviated = r.getCommit().abbreviate(8).name();
+    String abbreviated = abbreviateName(r.getCommit(), 8);
     String c = command(r, "tar.xz", abbreviated);
 
     try (InputStream out =
@@ -130,7 +131,7 @@
 
   private void assertArchiveNotPermitted() throws Exception {
     PushOneCommit.Result r = createChange();
-    String abbreviated = r.getCommit().abbreviate(8).name();
+    String abbreviated = abbreviateName(r.getCommit(), 8);
     String c = command(r, "zip", abbreviated);
 
     InputStream out =

diff --git a/javatests/com/google/gerrit/git/BUILD b/javatests/com/google/gerrit/git/BUILD
index d57d73f..ca272b2 100644
--- a/javatests/com/google/gerrit/git/BUILD
+++ b/javatests/com/google/gerrit/git/BUILD

@@ -31,6 +31,7 @@
         "//java/com/google/gerrit/testing:gerrit-test-util",
         "//lib:guava",
         "//lib/jgit/org.eclipse.jgit:jgit",
+        "//lib/jgit/org.eclipse.jgit.junit:junit",
         "//lib/truth",
     ],
 )

diff --git a/javatests/com/google/gerrit/git/ObjectIdsTest.java b/javatests/com/google/gerrit/git/ObjectIdsTest.java
new file mode 100644
index 0000000..cc7dde1
--- /dev/null
+++ b/javatests/com/google/gerrit/git/ObjectIdsTest.java

@@ -0,0 +1,103 @@
+// Copyright (C) 2019 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.git;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.common.truth.Truth.assert_;
+import static com.google.gerrit.git.ObjectIds.abbreviateName;
+
+import org.eclipse.jgit.internal.storage.dfs.DfsRepositoryDescription;
+import org.eclipse.jgit.internal.storage.dfs.InMemoryRepository;
+import org.eclipse.jgit.junit.TestRepository;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectReader;
+import org.eclipse.jgit.revwalk.RevBlob;
+import org.junit.Test;
+
+public class ObjectIdsTest {
+  private static final ObjectId ID =
+      ObjectId.fromString("0000000000100000000000000000000000000000");
+  private static final ObjectId AMBIGUOUS_BLOB_ID =
+      ObjectId.fromString("0000000000b36b6aa7ea4b75318ed078f55505c3");
+  private static final ObjectId AMBIGUOUS_TREE_ID =
+      ObjectId.fromString("0000000000cdcf04beb2fab69e65622616294984");
+
+  @Test
+  public void abbreviateNameDefaultLength() throws Exception {
+    assertRuntimeException(() -> abbreviateName(null));
+    assertThat(abbreviateName(ID)).isEqualTo("0000000");
+    assertThat(abbreviateName(AMBIGUOUS_BLOB_ID)).isEqualTo(abbreviateName(ID));
+    assertThat(abbreviateName(AMBIGUOUS_TREE_ID)).isEqualTo(abbreviateName(ID));
+  }
+
+  @Test
+  public void abbreviateNameCustomLength() throws Exception {
+    assertRuntimeException(() -> abbreviateName(null, 1));
+    assertRuntimeException(() -> abbreviateName(ID, -1));
+    assertRuntimeException(() -> abbreviateName(ID, 0));
+    assertRuntimeException(() -> abbreviateName(ID, 41));
+    assertThat(abbreviateName(ID, 5)).isEqualTo("00000");
+    assertThat(abbreviateName(ID, 40)).isEqualTo(ID.name());
+  }
+
+  @Test
+  public void abbreviateNameDefaultLengthWithReader() throws Exception {
+    assertRuntimeException(() -> abbreviateName(ID, null));
+
+    ObjectReader reader = newReaderWithAmbiguousIds();
+    assertThat(abbreviateName(ID, reader)).isEqualTo("00000000001");
+  }
+
+  @Test
+  public void abbreviateNameCustomLengthWithReader() throws Exception {
+    ObjectReader reader = newReaderWithAmbiguousIds();
+    assertRuntimeException(() -> abbreviateName(ID, -1, reader));
+    assertRuntimeException(() -> abbreviateName(ID, 0, reader));
+    assertRuntimeException(() -> abbreviateName(ID, 41, reader));
+    assertRuntimeException(() -> abbreviateName(ID, 5, null));
+
+    String shortest = "00000000001";
+    assertThat(abbreviateName(ID, 1, reader)).isEqualTo(shortest);
+    assertThat(abbreviateName(ID, 7, reader)).isEqualTo(shortest);
+    assertThat(abbreviateName(ID, shortest.length(), reader)).isEqualTo(shortest);
+    assertThat(abbreviateName(ID, shortest.length() + 1, reader)).isEqualTo("000000000010");
+  }
+
+  @FunctionalInterface
+  private interface Func {
+    void call() throws Exception;
+  }
+
+  private static void assertRuntimeException(Func func) throws Exception {
+    try {
+      func.call();
+      assert_().fail("Expected RuntimeException");
+    } catch (RuntimeException e) {
+      // Expected.
+    }
+  }
+
+  private static ObjectReader newReaderWithAmbiguousIds() throws Exception {
+    // Recipe for creating ambiguous IDs courtesy of git core:
+    // https://github.com/git/git/blob/df799f5d99ac51d4fc791d546de3f936088582fc/t/t1512-rev-parse-disambiguation.sh
+    TestRepository<?> tr =
+        new TestRepository<>(new InMemoryRepository(new DfsRepositoryDescription("repo")));
+    String blobData = "0\n1\n2\n3\n4\n5\n6\n7\n8\n9\n\nb1rwzyc3\n";
+    RevBlob blob = tr.blob(blobData);
+    assertThat(blob.name()).isEqualTo(AMBIGUOUS_BLOB_ID.name());
+    assertThat(tr.tree(tr.file("a0blgqsjc", blob)).name()).isEqualTo(AMBIGUOUS_TREE_ID.name());
+    return tr.getRevWalk().getObjectReader();
+  }
+}