Split mount directives on the first equals sign

[devops-thiago]

Type of Change

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

Motivation and Context

Fixes #2012.

Parser.mount splits each comma-separated directive with maxSplits: 2. In Swift that parameter counts splits rather than resulting elements, so a value that itself contains an equals sign produces three components:

"src=/tmp/a=b".split(separator: "=", maxSplits: 2)
// ["src", "/tmp/a", "b"]

The parser then requires exactly two components and throws invalid directive format missing value. Equals signs are legal in POSIX path names, so a bind mount whose source or destination contains one cannot be used today.

Splitting on the first equals sign keeps the remainder as the value. Directives that carry no value, such as readonly, still produce a single component and are unaffected.

#1978 and #1999 fix the same defect in Parser.labels. Neither changes Parser.mount.

Testing

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

testMountBindSourceContainingEquals creates a directory whose name contains an equals sign and mounts it by absolute path. Against the current code the test fails with invalid directive format missing value; with this change it passes. The existing mount and publish-port tests continue to pass.

I also ran a debug build of this branch against a 1.5.0 daemon with the command from the issue. The 1.5.0 release and a build of main fail with invalid directive format missing value. This branch starts the container, and mount inside it shows virtiofs on /mnt type virtiofs (rw,relatime).

[devops-thiago]

Asking a few more people for review. I previously requested reviews from @egernst and @jglogan on #2019, but haven’t heard back, and CONTRIBUTING suggests trying someone else after a few weeks.

The only review so far is katiewasnothere’s on #2329 — thanks. I replied there.

I have 11 small PRs open. CI has not run on any of them because the workflows are still waiting for approval (action_required). Approving those runs would at least show whether they pass.

I tried to match each PR to areas you’ve worked on, but anyone is welcome to review any of them:

• @dkovba: Validate XPC peers with xpc_connection_get_euid instead of the non-public audit-token API #2091 — remove the non-public audit-token call from XPCServer
• @JaewonHur: Report an unreadable build context as permission denied, not a missing Dockerfile #2093 — report when a build context cannot be read; Persist container exit codes and surface them on ContainerSnapshot #2090 — preserve a container’s exit code across an apiserver restart ([Request]: Surface lastExitCode on ContainerSnapshot #1501); Move the export into place with rename() instead of deleting first #2329 — make export -o refuse an existing directory instead of deleting it
• @realrajaryan: Split mount directives on the first equals sign #2016, Keep the trailing equals sign out of parsed key names #2017, Accept port 1 when validating published port ranges #2018 — small parser fixes, each with a test; Hide infrastructure images by repository, not exact reference #2092 — hide infrastructure images by repository; Require an absolute destination for bind and volume mounts #2328 — reject a relative mount destination, matching --tmpfs
• @crosbymichael: Keep the installed kernel when a forced replacement fails to copy #2330 — avoid deleting the installed kernel when kernel set --force fails; Fail a download that stops receiving data #2331 — avoid hanging during a kernel download when the server stops sending data

All commits are signed and the branches are rebased on main.

For each bug, I reproduced the issue on the 1.5.0 release and included the output in the PR. I also tested each fix from a build of its branch.

Those fixes started as fixes in the engine used by SiliconShip, a Mac app I build: https://apps.apple.com/app/id6797506428.

I’m happy to split, shrink, or close any of these if that would make review easier.

[github-actions]

Code Coverage

Tier	Line Coverage
Unit	25.35%
Integration	66.3%
Combined	75.8%

[devops-thiago]

@dkovba thank you for approving the workflows. CI passes on this PR and it still merges cleanly into main. Is it good to merge as it is, or is there anything else you need from me?

[devops-thiago]

@katiewasnothere this has been open since Jul 25 without a review. CI passes and it merges cleanly into main. Could you take a look when you have time, or tell me who else I should ask?