Unifying git branch -l, git tag -l, and git for-each-ref

by Karthik Nayak for Git

`git branch -l`, `git tag -l` and `git for-each-ref` are all about selecting a set of refs and printing the result. Currently, each has their own implementation and options. This results in some of them having selection options and others having formatting options. I propose to build a common library so that all three commands have common options and use the library extensively throughout their code.