Document why the repository is large and how to shrink a clone

[berendt]

A full clone of this repository uses around 500 MB of disk space, which is surprising for a documentation site whose source tree is a few MB. Nothing in the working tree explains it, so this adds a Repository Size section to the README that does.

The cause is the gh-pages branch. The deploy workflow pushes the complete rendered site there on every build, and 391515 of the 399118 objects in the pack belong to that branch alone, 98% of the repository. The two Docusaurus search indexes account for roughly 270 MB across 1582 stored versions: they are minified JSON with regenerated term IDs, so nearly the whole file changes per build and Git cannot store the versions as small deltas. The rendered HTML under docs/ and de/docs/ adds another 145 MB.

Nobody working on the site needs gh-pages locally, so the section gives both ways to avoid it, either dropping the remote-tracking ref and repacking an existing clone, or cloning with --single-branch from the start. Both leave the clone at around 20 MB, measured with a --single-branch clone of main.

The negative refspec that keeps git fetch from restoring the branch needs Git 2.29 or newer, and the section says so along with how to undo it. It also states that this is local only, so that nobody reads the instructions as a change that would break GitHub Pages.

README only, no site content and no workflow is touched.

[github-actions]

✅⚠️MegaLinter analysis: Success with warnings

Descriptor	Linter	Files	Fixed	Errors	Max errors	Warnings	Elapsed time
✅ ACTION	actionlint	5		0		0	0.04s
✅ JSON	jsonlint	4		0		0	0.08s
✅ JSON	prettier	4		0		0	0.26s
✅ JSON	v8r	4		0		0	8.19s
✅ MARKDOWN	markdownlint	169		0		0	1.54s
✅ MARKDOWN	markdown-table-formatter	169		0		0	0.22s
✅ REPOSITORY	betterleaks	yes		no		no	0.49s
✅ REPOSITORY	checkov	yes		no		no	18.77s
✅ REPOSITORY	git_diff	yes		no		no	0.04s
✅ REPOSITORY	secretlint	yes		no		no	2.36s
✅ REPOSITORY	trufflehog	yes		no		no	3.35s
✅ SPELL	codespell	179		0		0	0.4s
⚠️ SPELL	lychee	179		1		0	37.9s
✅ YAML	prettier	6		0		0	0.25s
✅ YAML	v8r	6		0		0	5.31s
✅ YAML	yamllint	6		0		0	0.69s

Detailed Issues

⚠️ SPELL / lychee - 1 error

📝 Summary
---------------------
🔍 Total.........1082
🔗 Unique.........823
✅ Successful....1007
⏳ Timeouts.........3
🔀 Redirected.......5
👻 Excluded........71
❓ Unknown..........0
🚫 Errors...........1
⛔ Unsupported......1

Errors in docs/guides/deploy-guide/services/openstack.md
[TIMEOUT] https://www.openstack.org/software/project-navigator/openstack-components#openstack-services (at 14:5) | Request timed out

Errors in docs/release-notes/osism-10.md
[ERROR] https://gateway-api.sigs.k8s.io/ (at 842:3) | Connection failed. Check network connectivity and firewall settings

Errors in docs/release-notes/osism-7.md
[TIMEOUT] https://www.openstack.org/software/openstack-bobcat (at 978:38) | Request timed out

Errors in docs/release-notes/osism-8.md
[TIMEOUT] https://www.openstack.org/software/openstack-caracal (at 223:38) | Request timed out

Hint: Followed 5 redirects. You might want to consider replacing redirecting URLs with the resolved URLs. Use verbose mode (`-v`/`-vv`) to see redirection details.

See detailed reports in MegaLinter artifacts

Your project could benefit from a custom flavor, which would allow you to run only the linters you need, and thus improve runtime performances. (Skip this info by defining FLAVOR_SUGGESTIONS: false)

• Documentation: Custom Flavors
• Command: npx mega-linter-runner@10.0.0 --custom-flavor-setup --custom-flavor-linters ACTION_ACTIONLINT,JSON_JSONLINT,JSON_V8R,JSON_PRETTIER,MARKDOWN_MARKDOWNLINT,MARKDOWN_MARKDOWN_TABLE_FORMATTER,REPOSITORY_CHECKOV,REPOSITORY_GIT_DIFF,REPOSITORY_BETTERLEAKS,REPOSITORY_SECRETLINT,REPOSITORY_TRUFFLEHOG,SPELL_LYCHEE,SPELL_CODESPELL,YAML_PRETTIER,YAML_YAMLLINT,YAML_V8R

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[jklare]

lgtm