Backport #15432
There is a weird gotcha with GetTagCommitID that because it uses git rev-list
can cause an ambiguous argument error.
This PR simply makes tags use the same code as branches.
Signed-off-by: Andrew Thornton <art27@cantab.net>
This module is merged from https://github.com/go-gitea/git which is a Go module to access Git through shell commands. Now it's a part of gitea's main repository for easier pull request.