Feature Requests:Try shallow git clones as much as possible

[xuzhongping]

Hi, I noticed that now when there is a branch or tag in the parameter it will do a shallow clone, if the parameter is a commit, I think I can try to check if there is a branch head or tag that can be mapped to this commit such as git ls-remote, which can Use shallow clones whenever possible to reduce download times.
(Note that this modification should not break the existing cocoapods git cache)

[FKREISE]

+100000 on this issue. Currently, for every pod update we have to download over 500 MB of data because our default branch during development is not master.