Hello,

First, thank you for maintaining and developing this nice Git plugin!

Recently, I got some issues with some jobs using a wrong refspec to build. This only happened recently for jobs doing a "frech clone" and I suspect, only after an update of the Git Plugin.

I don't have the issue when enabling "Preserve second fetch during checkout" option from PR-845 (JENKINS-49757).

Maybe what is particular on my side is that there are multiple branches in my repo and my refspec contains 'refs/heads' ("refs/heads/mptcp_trunk/master"). From what I see in PR-845, that's why the second fetch is not done but I don't know why it is an issue to add 'refs/heads' in the refspec. When I look at what is done by Jenkins, it looks like I could only add the name of the branch but if I have not to specified 'refs/heads', I am confused with the option name and the description
Also, I didn't set anything related to "Advanced Clone Option" as mentioned in the doc because I didn't find the corresponding option in the config (and to be honest, I don't know why I would like to do the clone and the fetch later differently ).

(Note: I added "origin/" in the branch name just to try but it didn't help. Just to explain why we see a reference to "origin/xxx" in the logs)

Here are the logs without "Preserve second fetch during checkout" option:

 > git fetch --tags --progress ssh://gerrit:29418/repo.git +refs/heads/*:refs/remotes/origin/* # timeout=10
 > git config remote.origin.url ssh://gerrit:29418/repo.git # timeout=10
 > git config --add remote.origin.fetch +refs/heads/*:refs/remotes/origin/* # timeout=10
Avoid second fetch
 > git rev-parse FETCH_HEAD^{commit} # timeout=10
Checking out Revision 5ac0ebcbb890f2a7852bca357641163837a219bd (origin/mptcp_trunk/master)
 > git config core.sparsecheckout # timeout=10
 > git checkout -f 5ac0ebcbb890f2a7852bca357641163837a219bd # timeout=10
Commit message: "old commit"

Here, you can see that all branches are fetches but then FETCH_HEAD is used with git checkout which is not correct: FETCH_HEAD corresponds to the first branch by alphabetical order on the remote (because we asked for refs/heads/*).

Now here is the output with "Preserve second fetch during checkout" on:

 > git fetch --tags --progress ssh://gerrit:29418/repo.git +refs/heads/*:refs/remotes/origin/* # timeout=10
 > git config remote.origin.url ssh://gerrit:29418/repo.git # timeout=10
 > git config --add remote.origin.fetch +refs/heads/*:refs/remotes/origin/* # timeout=10
 > git config remote.origin.url ssh://gerrit:29418/repo.git # timeout=10
Fetching upstream changes from ssh://gerrit:29418/repo.git
using GIT_SSH to set credentials 
 > git fetch --tags --progress ssh://gerrit:29418/repo.git refs/heads/mptcp_trunk/master +refs/heads/mptcp_trunk/master:refs/remotes/origin/mptcp_trunk/master # timeout=10
 > git rev-parse FETCH_HEAD^{commit} # timeout=10
Checking out Revision 21ec2388799b5bd7e18f3f2bd4aa7f0e2be9bb23 (origin/mptcp_trunk/master)
 > git config core.sparsecheckout # timeout=10
 > git checkout -f 21ec2388799b5bd7e18f3f2bd4aa7f0e2be9bb23 # timeout=10
Commit message: "new commit"

FETCH_HEAD is now corresponding to refs/heads/mptcp_trunk/master, what I want: then everything is OK.

I hope this will help finding the issue not to have to enable "Preserve second fetch during checkout" option.