[soulteary]

A custom DOWNLOAD_URL or REPO_FILE containing spaces or shell metacharacters can split the RPM repository URL into multiple arguments or be interpreted by the inner sh -c. Even the existing dnf5 single quotes break when the URL contains an apostrophe.

This change quotes the assembled URL as one literal POSIX shell argument for dnf5, dnf and yum-config-manager. Embedded apostrophes, double quotes, dollar expressions and backticks remain part of the argument.

What changed

• Add a small POSIX shell quoting helper and apply it to the three current RPM repository-add commands.
• Preserve repository filename defaults, mirror precedence, channel handling and package-manager selection.
• Add an independent offline CI job and document the regression suite.

The implementation is inspired by docker/docker-install#449. It applies the quoting fix to the current code and does not restore the obsolete dnf5 temporary-file workaround.

Verification

The regression suite executes the installer's generated commands through the selected shell into inert package-manager mocks, then compares their exact argument arrays. Host detection is controlled by the harness; repository command generation comes from the installer.

Each run covers 48 cases across dnf5, dnf and yum and both stable/test channels: default and staging URLs, custom URL/repository filename combinations, mirror precedence, whitespace, single/double quotes, literal $HOME, $(), backticks and newlines. Marker files confirm that the embedded command substitutions are not executed.

Passed locally:

python3 scripts/test-repository-url-quoting.py
TEST_SHELL=dash python3 scripts/test-repository-url-quoting.py
TEST_SHELL=bash python3 scripts/test-repository-url-quoting.py
sh -n install.sh
bash -n install.sh
make shellcheck STABLE_LATEST=29.4.2 TEST_LATEST=29.4.2 'SHELLCHECK=shellcheck -e SC1091,SC1117,SC2317,SC2329'
git diff --check

The new regression was run before the fix and failed on the dnf5 custom URL containing an apostrophe with an inner-shell syntax error. It passes with the fix. The fixed version values above are offline build fixtures; ShellCheck 0.11.0 was used locally.

These checks made no network requests, installed no packages and changed no host repository files. They verify argument transport; live RPM repository availability and package-manager compatibility require their respective Linux environments. The existing installation CI remains applicable.

Submission

This PR targets soulteary/docker-install:main. The commit is DCO signed off. A separate branch contains this change without the fork's mirror additions, based on upstream master; open the upstream comparison for manual submission. No upstream PR has been created.