Integration test demonstrating support for multiple tags with same name

Summary:
The earlier versions of `gitimport` didn't used to peel tags when trying to upload the tag contents. With that version, it was possible to have the below scenario work for gitimport but fail for Mononoke Git server:
- Create tag A point to commit C
- Created another tag with the same name A and point it to the object id of the old tag A
- gitimport the repo

The earlier version of gitimport would only import the new tag A without uploading the git object corresponding to the old tag A. On Mononoke server when performing the clone, we would try to peel the tags and return everything referenced by it only to find the inner tag missing and would error out. This actually happened in production for `whatsapp/android` repo since it was imported early last year.

In the current version of gitimport, this bug is fixed so this integration test serves as protection against regression and as a proof that we support this particular use-case

Reviewed By: markbt

Differential Revision: D75964395

fbshipit-source-id: 29835270ea9915b4cccf938fdc4881ade5fc607b

Author: RajivTS

eden/mononoke/tests/integration/mononoke_git_server/test-mononoke-git-server-clone-with-duplicate-tags.t

@@ -0,0 +1,57 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License found in the LICENSE file in the root
+# directory of this source tree.
+
+  $ . "${TEST_FIXTURES}/library.sh"
+  $ REPOTYPE="blob_files"
+  $ setup_common_config $REPOTYPE
+  $ GIT_REPO_ORIGIN="${TESTTMP}/origin/repo-git"
+  $ GIT_REPO="${TESTTMP}/repo-git"
+
+# Setup git repository
+  $ mkdir -p "$GIT_REPO_ORIGIN"
+  $ cd "$GIT_REPO_ORIGIN"
+  $ git init -q
+  $ echo "this is file1" > file1
+  $ git add file1
+  $ git commit -qam "Add file1"
+  $ git tag -a -m "new tag" first_tag
+  $ git config advice.nestedTag false
+  $ git tag -a -m "new tag" -f first_tag first_tag
+  Updated tag 'first_tag' (was 8963e1f)
+  $ echo "this is file2" > file2
+  $ git add file2
+  $ git commit -qam "Add file2"
+  $ git tag -a empty_tag -m ""
+  $ cd "$TESTTMP"
+  $ git clone "$GIT_REPO_ORIGIN"
+  Cloning into 'repo-git'...
+  done.
+
+# Capture all the known Git objects from the repo
+  $ cd $GIT_REPO
+  $ git rev-list --objects --all | git cat-file --batch-check='%(objectname) %(objecttype) %(rest)' | sort > $TESTTMP/object_list
+
+# Import it into Mononoke
+  $ cd "$TESTTMP"
+  $ quiet gitimport "$GIT_REPO" --derive-hg --generate-bookmarks full-repo
+
+# Start up the Mononoke Git Service
+  $ mononoke_git_service
+# Clone the Git repo from Mononoke
+  $ git_client clone $MONONOKE_GIT_SERVICE_BASE_URL/$REPONAME.git
+  Cloning into 'repo'...
+  remote: Converting HAVE Git commits to Bonsais        
+  remote: Converting WANT Git commits to Bonsais        
+  remote: Collecting Bonsai commits to send to client        
+  remote: Counting number of objects to be sent in packfile        
+  remote: Generating trees and blobs stream        
+  remote: Generating commits stream        
+  remote: Generating tags stream        
+  remote: Sending packfile stream        
+# Verify that we get the same Git repo back that we started with
+  $ cd $REPONAME  
+  $ git rev-list --objects --all | git cat-file --batch-check='%(objectname) %(objecttype) %(rest)' | sort > $TESTTMP/new_object_list
+  $ diff -w $TESTTMP/new_object_list $TESTTMP/object_list