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It seems like there was some upgrade of a golang interpretation of the
format argument. This patch solves the mismatch.

The fix script was only supposed to replace the FROM definitions of
pinned versions. Due to a wrong regex it ended up always stripping the
tag or version definition resulting in wrong builds.

This patch fixes the problem and adds a test to prevent such issues in
future.

This patch adds a test for the newly introduced fix-dockerfile.sh, which
is supposed to remove the tag information from pinnned repositories.

While maintaining only-tagged image references as they are.

Currently podman doesn't allow to handle pinned container images in FROM
statements if they also contain a tag.

Example:

```
FROM docker.io/library/haproxy:1.9.15-alpine@sha256:1da27f6d19b52d85c3c31412f2e387be54b4cddba938d68ec6b24775bd89d75c
```

Will be refused with the following error message:

```
Error: error creating build container: error parsing attempted image name "docker://docker.io/library/haproxy:1.9.15-alpine@sha256:1da27f6d19b52d85c3c31412f2e387be54b4cddba938d68ec6b24775bd89d75c": Docker references with both a tag and digest are currently not supported
```

If you remove the tag reference `:1.9.15-alpine`, things will work fine:

```
FROM docker.io/library/haproxy@sha256:1da27f6d19b52d85c3c31412f2e387be54b4cddba938d68ec6b24775bd89d75c
```

And that's what this tool is for. It's intended to run before starting
`podman build .` in order to "fix" the Dockerfile first and then run a
regular build without losing any of the useful information about which
tag this image is supposed to be based on.

This minimal CLI provides an universal and easy way to push images that
were tagged using si-tagging to upstream repositories.