Version not available in Docker image

[claabs]

Describe the bug

The Docker image does not contain the app version data, causing some links to break.

The root issue is that the Makefile depends on a git command to get the rev, and the Docker builder ignores the .git folder. You can see the error here: https://github.com/writefreely/writefreely/actions/runs/7758253252/job/21159589862#step:5:365

I recommend adding a fallback to an git rev environment variable that is set in the Docker build action.

Steps to reproduce (if necessary)

Steps to reproduce the behavior:

1. Run in the official Docker image
2. Go to https://example.com/admin
3. Observe the footer links to https://writefreely.org/guide/v and says "writefreely v"

Expected behavior

It should say the version number in the footer

Application configuration

• Single mode
• Database? sqlite
• Open registration? no
• Federation enabled? yes

Version or last commit: ghcr.io/writefreely/writefreely:v0.15.0

[claabs]

Oh, the lack of git also causes issues with scripts/invalidate-css.sh, which explains why my login page has no CSS.