fast-import fails with case sensitive tags due to case insensitive lock files

Hi,

I have a problem with fast-import on an NTFS drive: If I try to import tags which are identical apart from their casing a failure due to identical lock file names occurs.

I am running git for windows 2.15.1.2 x64 on a Windows 10 machine (10.0.15063): $ git --version --build-options git version 2.15.1.windows.2 built from commit: 5d5baf91824ec7750b103c8b7c4827ffac202feb sizeof-long: 4 machine: x86_64

MCVE:
 (echo "commit refs/heads/master" && 
 echo "mark :1" &&
 echo "committer me <> 0 +0000" &&
 echo "data 0" &&
 echo "" &&
 echo "tag tag_A" &&
 echo "from :1" &&
 echo "tagger me <> 0 +0000" &&
 echo "data 0" &&
 echo "" &&
 echo "tag tag_a" &&
 echo "from :1" &&
 echo "tagger me <> 0 +0000" &&
 echo "data 0" &&
 echo "") | git fast-import

Instead of having 1 commit with two tags ("tag_A" and "tag_a") I get his error message: Unpacking objects: 100% (4/4), done. error: cannot lock ref 'refs/tags/tag_a': Unable to create 'C:/tmp/.git/refs/tags/tag_a.lock': File exists.

Another git process seems to be running in this repository, e.g. an editor opened by 'git commit'. Please make sure all processes are terminated then try again. If it still fails, a git process may have crashed in this repository earlier: remove the file manually to continue.

Best regards, Jonathan