Fix tmpfs mount source field left empty for --mount type=tmpfs

[sivasath16]

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Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Motivation and Context

Fixes #2109.

Filesystem.source is left empty when a tmpfs mount is created via --mount type=tmpfs,..., which corrupts its entry in
/proc/mounts and breaks df (df: tmpfs: No such file or directory) and mount, both of which parse that line positionally.

Parser.mount() sets Filesystem.type for type=tmpfs but never sets Filesystem.source. The --tmpfs flag doesn't have this problem because it builds its Filesystem via Filesystem.tmpfs(), which already hardcodes source: "tmpfs".

This sets source the same way in Parser.mount(), so both paths agree.

Testing

• Tested locally
• Added/updated tests
• Added/updated docs

Before / after

Added testRunCommandMountTmpfs, which runs a real container with --mount type=tmpfs,... and checks df and /proc/mounts.

Before the fix:

✘ Test testRunCommandMountTmpfs() failed after 2.168 seconds with 1 issue.

After the fix:

✔ Test testRunCommandMountTmpfs() passed after 2.124 seconds.

Also ran the full targeted suites on the final diff:

• swift test --filter ParserTest — 138/138 passed
• CONTAINER_CLI_PATH=$(pwd)/bin/container swift test --filter TestCLIRunCommand — 33/33 passed

[sivasath16]

Hi @egernst, this is ready for review. I added the fix for #2109 along with parser regression coverage and an integration test that reproduces the df failure before the fix and passes after it.

I also included the before/after results in the PR description as requested.

Thanks!

[rupinajay]

LGTM

[sivasath16]

Hi @egernst ! When you get a chance, could you please review this? Thank you!

[egernst]

@sivasath16, please sign your commits. See:

• https://github.com/apple/containerization/blob/main/CONTRIBUTING.md#pull-requests
• https://docs.github.com/en/authentication/managing-commit-signature-verification/signing-commits

[sivasath16]

Hi @egernst, Signed the commit. Thanks!