[2014-12-18 13:04:49,814] ERROR com.google.gerrit.sshd.BaseCommand : Internal server error (user XXX account 1000017) during git-receive-pack '/projectname1/module1'
com.google.gerrit.sshd.BaseCommand$Failure: fatal: Unpack error, check server log
        at com.google.gerrit.sshd.commands.Receive.runImpl(Receive.java:176)
        at com.google.gerrit.sshd.AbstractGitCommand.service(AbstractGitCommand.java:101)
        at com.google.gerrit.sshd.AbstractGitCommand.access$000(AbstractGitCommand.java:32)
        at com.google.gerrit.sshd.AbstractGitCommand$1.run(AbstractGitCommand.java:70)
        at com.google.gerrit.sshd.BaseCommand$TaskThunk.run(BaseCommand.java:442)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
        at java.util.concurrent.FutureTask.run(FutureTask.java:262)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:178)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:292)
        at com.google.gerrit.server.git.WorkQueue$Task.run(WorkQueue.java:364)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:745)
Caused by: java.io.IOException: Unpack error on project "projectname1/module1":
  AdvertiseRefsHook: org.eclipse.jgit.transport.AdvertiseRefsHookChain@2453e48cclass org.eclipse.jgit.transport.AdvertiseRefsHookChain

        at com.google.gerrit.sshd.commands.Receive.runImpl(Receive.java:175)
        ... 12 more
Caused by: org.eclipse.jgit.errors.UnpackException: Exception while parsing pack stream
        at org.eclipse.jgit.transport.ReceivePack.service(ReceivePack.java:239)
        at org.eclipse.jgit.transport.ReceivePack.receive(ReceivePack.java:160)
        at com.google.gerrit.sshd.commands.Receive.runImpl(Receive.java:115)
        ... 12 more
Caused by: org.eclipse.jgit.errors.CorruptObjectException: Invalid tree a33cf05e7a: duplicate entry names
        at org.eclipse.jgit.transport.PackParser.verifySafeObject(PackParser.java:1017)
        at org.eclipse.jgit.transport.PackParser.whole(PackParser.java:998)
        at org.eclipse.jgit.transport.PackParser.indexOneObject(PackParser.java:916)
        at org.eclipse.jgit.transport.PackParser.parse(PackParser.java:487)
        at org.eclipse.jgit.internal.storage.file.ObjectDirectoryPackParser.parse(ObjectDirectoryPackParser.java:194)
        at org.eclipse.jgit.transport.BaseReceivePack.receivePack(BaseReceivePack.java:1020)
        at org.eclipse.jgit.transport.BaseReceivePack.receivePackAndCheckConnectivity(BaseReceivePack.java:848)
        at org.eclipse.jgit.transport.ReceivePack.service(ReceivePack.java:191)
        ... 14 more
Caused by: org.eclipse.jgit.errors.CorruptObjectException: duplicate entry names
        at org.eclipse.jgit.lib.ObjectChecker.checkTree(ObjectChecker.java:388)
        at org.eclipse.jgit.lib.ObjectChecker.check(ObjectChecker.java:179)
        at org.eclipse.jgit.transport.PackParser.verifySafeObject(PackParser.java:1015)
        ... 21 more

You can clean your Git history of duplicate entries with the BFG:

https:// github.com/rtyley/bfg-repo-cleaner/releases/tag/v1.11.1

$ bfg --fix-filename-duplicates-preferring tree

Seasons greetings,
Roberto