fix(Dockerfile): initialize git repo in VMAF source to satisfy vcstagger

[cyberjames]

Summary:
This PR fixes the build error in the Dockerfile by initializing a minimal git repository in the VMAF source directory. The issue occurred during the Meson step (vcstagger) because the tarball lacked a .git folder.

Changes:

• Added commands to initialize a git repo and commit the extracted VMAF source before running Meson.
• This allows git describe to work correctly, resolving the fatal error during build.

Testing:
I built the image locally (using Podman on an Apple M3 Pro) and confirmed that the build now completes successfully without errors.

[wader]

Hi, could you elaborate more? i'm a bit confused as it seems to build fine as it is.

But i do see this in the build log but it seem to not fail the build? but maybe some version string ends up wrong or empty because of it, but is that string exposed somewhere via the ffmpeg cli tools?

2025-03-18T19:57:28.4166860Z #7 3.823 [64/93] /usr/bin/meson --internal vcstagger ../include/vcs_version.h.in include/vcs_version.h 3.0.0 /vmaf-3.0.0/libvmaf/include @VCS_TAG@ '(.*)' /usr/bin/git --git-dir /vmaf-3.0.0/libvmaf/../.git describe --tags --long --match '?.*.*' --always
2025-03-18T19:57:28.4168390Z #7 3.901 fatal: not a git repository: '/vmaf-3.0.0/libvmaf/../.git'

For what i can see vmaf does not do "proper" source distributions of releases that embed the version? the "source code" link on github will download a git tag.

[wader]

@cyberjames could you provide some more details?

[cyberjames]

Hey @wader , sorry for the delay! I was trying to remember the exact error but didn’t manage to capture the full logs.

I was mainly focused on adding those changes in the Dockerfile since it looked similar to what you posted.

Happy to cancel this PR if it’s not needed, just let me know what you reckon.

[wader]

No worries. So docker build failed? was that with some local changes? the current Dockerfile seems to build fine on my arm macbook