It should be 4 spaces... I found where the default is set, here's a
quick untested patch with no configurability.
You can also change your personal preferences under Differences ->
Preferences
diff --git
a/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/AccountDiffPreference.java
b/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/AccountDiffPreference.java
index 3b04725..5c689aa 100644
---
a/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/AccountDiffPreference.java
+++
b/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/AccountDiffPreference.java
@@ -58,7 +58,7 @@ public class AccountDiffPreference {
public static AccountDiffPreference createDefault(Account.Id
accountId) {
AccountDiffPreference p = new AccountDiffPreference(accountId);
p.setIgnoreWhitespace(Whitespace.IGNORE_NONE);
- p.setTabSize(8);
+ p.setTabSize(4);
p.setLineLength(100);
p.setSyntaxHighlighting(true);
p.setShowWhitespaceErrors(true);