Add tag in "export-subst" file

Question

Situation

We have a git workflow, where all release versions are stacked on the master branch, and when a commit is ready for deployment, we add a tag to it, then use git archive to build a bundle to be deployed.

We use a version.txt file, marked in .gitattributes with the option export-subst, to keep track of which commit was used to build a given archive.

Question

If I write $Format:%d$ in version.txt, and export a tagged commit, I will have something like (HEAD, tag, master) written in the resulting file.

How can I have the tag alone ?

[edit] There is a git command which already produces that :

git describe --tags HEAD

This will output :

latest_tag            #if HEAD is tagged

latest_tag-5-g03cc91b #if HEAD is not tagged,
                      #and the latest tag is 5 commits ago on commit g03cc91b

Is there some way to have a slug replaced with this output in version.txt ?

Answer 1

You could use a content filter driver which would on git checkout automatically do the exact change you want.

^{(From Pro Git book 7.2 Customizing Git - Git Attributes)}

You declare in a .gitattributes file a smudge script which will do the substitution for a special marker (that you want to be replaced with git describe --tags HEAD), without touching the other markers to be modified by export-subst on git archive.

Then you call git archive, which should (not tested) replace the rest.