Dockerfile broken with ARTIFACT_BASE=sagemath/sagemath-dev:develop

[rrueger]

Environment

• OS: Archlinux / 6.12.16-1-lts
• Sage Version: Commit 9cd86e95 (git log -1 --format=%H | head -c8)

Steps To Reproduce

On the one hand, the Dockerfile itself suggests to speed up build times by basing on e.g. sagemath/sagemath-dev:develop

sage/docker/Dockerfile

Lines 34 to 35 in 9cd86e9

	# To build Sage, run this command from your sage/ directory: #
	# $ docker build --build-arg MAKEFLAGS="-j4" --build-arg SAGE_NUM_THREADS="4" --build-arg ARTIFACT_BASE="sagemath/sagemath-dev:develop" -f docker/Dockerfile --target=make-build --tag sage .

On the other hand, the Dockerfile also says

sage/docker/Dockerfile

Lines 134 to 136 in 9cd86e9

	# Warning: If you set ARTIFACT_BASE to something else than source-clean, the #
	# build is not going to use the build-time-dependencies target but rely on #
	# whatever tools are installed in ARTIFACT_BASE. #

and a few lines lower

sage/docker/Dockerfile

Lines 154 to 159 in 9cd86e9

	ARG SAGE_ROOT=/home/sage/sage
	WORKDIR $SAGE_ROOT
	# We create a list of all files present in the artifact-base (with a timestamp
	# of now) so we can find out later which files were added/changed/removed.
	RUN find . \( -type f -or -type l \) > $HOME/artifact-base.manifest
	RUN git fetch --update-shallow "$HOME/sage-context" HEAD \

assumes that /home/sage/sage is a git repository.

This doesn't appear to be the case for any of the sagemath/sagemath*:* images

# docker run sagemath/sagemath-dev:develop git -C /home/sage/sage/.git status
fatal: cannot change to '/home/sage/sage/.git': No such file or directory

As a result, this kind of build fails. For now I will build from source-clean.

Config log

n/a

Package logs

n/a

Additional Information

No response

Checklist

• I have searched the existing issues for a bug report that matches the one I want to file, without success.
• I have read the documentation and troubleshoot guide