Ensure backslashes in windows filename

[stefansli]

cmd.exe doesn't work with '/' as path separator.

JENKINS-72044 - Fix filepath on windows

With #1443 the GIT_ASKPASS script was changed. Unfortunately the .bat script contains / instead of \ on Windows. While / generally works as path separator on Windows, it does not work with cmd.exe.

Checklist

• [x] I have read the CONTRIBUTING doc
• [x] I have referenced the Jira issue related to my changes in one or more commit messages
• [x] No Javadoc warnings were introduced with my changes
• [x] No spotbugs warnings were introduced with my changes
• [x] I have interactively tested my changes

Types of changes

What types of changes does your code introduce? Put an x in the boxes that apply. Delete the items in the list that do not apply

• [x] Bug fix (non-breaking change which fixes an issue)

Further comments

This is a small change that fixes a bug introduced in 5.2.0 making the gitUsernamePassword binding unuseable on windows agents.

[stefansli]

@jenkinsci/git-plugin-developers any timeline when this will be looked at and merged? Maybe @MarkEWaite ?

[MarkEWaite]

I am out of the country currently. Once I return there are several reviews that will precede this one

[ysmaoui]

workaround until this PR is merged

withCredentials([gitUsernamePassword(credentialsId: 'myUsernameTokenCredentialsID', gitToolName: 'git-tool')]) {
    
    // (ugly) workaround for https://issues.jenkins.io/browse/JENKINS-72044
    // until this PR is merged https://github.com/jenkinsci/git-plugin/pull/1555
    powershell("""
        (Get-Content \$Env:GIT_ASKPASS).Replace('/', '\\') | Set-Content \$Env:GIT_ASKPASS
    """)

    powershell("""
            git clone https://my/orga/repo.git
        """
    )
}