How to programmatically determine whether the Git checkout is a tag and if so, what is the tag name

Question

In a Unix or GNU scripting environment (e.g. a Linux distro, Cygwin, OSX), what is the best way to determine whether the current checkout is a Git tag. If it is a tag, how c

Answer 1

A better solution (from Greg Hewgill's answer in the other question) would be:

git name-rev --name-only --tags HEAD

If it returns "undefined" then you are not on a tag. Otherwise it returns the tag name. So a one-liner to do something like my other answer would be:

git_tag=`git name-rev --name-only --tags HEAD | sed 's/^undefined$//'`

Interactive shell example of how it works:

$ git checkout master
Already on "master"
$ git name-rev --name-only --tags HEAD
undefined
$ git checkout some-tag
Note: moving to "some-tag" which isnt a local branch
If you want to create a new branch from this checkout, you may do so
(now or later) by using -b with the checkout command again. Example:
  git checkout -b 
HEAD is now at 1234567... Some comment blah blah
$ git name-rev --name-only --tags HEAD
some-tag