sandboxes: document branch-mode in-container clone and source-repo isolation#25007
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sandboxes: document branch-mode in-container clone and source-repo isolation#25007ndeloof wants to merge 1 commit into
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Assessment: 🟢 APPROVE
The documentation changes are well-written and follow Docker's style guidelines. The branch-mode section rewrite, source-repository isolation explanation, and security model updates are clear, accurate, and appropriately scoped.
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Assessment: 🟢 APPROVE
The PR is well-structured and clearly documents the branch-mode in-container clone and source-repository isolation. Content is accurate and the technical explanations are thorough. A few minor style guide violations in the added content.
…olation Update the branch-mode workflow to reflect the move from on-host worktrees to an in-container clone exposed over git-daemon, and add a new source-repository isolation layer to the security model. Highlights the strong guarantee that an unconstrained agent cannot corrupt the host's .git directory or working tree, since the source mount is read-only and the agent operates on a private clone with its own index, refs, and working tree. Tracks docker/sandboxes#2477.
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… isolation Replaces the `--branch[=NAME]` documentation with `--clone` (boolean) on both `sbx create` and `sbx run`, matching the CLI rename in docker/sandboxes#3055. Clone mode is now strictly about running the agent on a private in-container `git clone --reference` of the host repository; no host-side branch is created on the user's behalf — the user instructs the agent to `git checkout -b ...` inside the sandbox if a dedicated working branch is needed. Key documentation changes: - usage.md: "Branch mode" section is renamed to "Clone mode" and rewritten end-to-end. Drops the `.sbx/<name>-worktrees/...` directory mention (no longer created), the host-side branch creation/checkout step, the `--branch=auto` flow, and the legacy "Multiple branches per sandbox" section. Adds: * an explicit note that clone mode is fixed at create time; * the forge-remote propagation behaviour (origin/upstream propagated from host into the in-container clone, local-path remotes skipped); * a Cleanup warning about lost in-container commits when running `sbx rm` (mirrors the runtime warning). - security/isolation.md: adds the "Source-repository isolation" section introduced in docker#25007. Same content, but uses `--clone` and "clone mode" terminology throughout, plus a clarifying note that `sbx rm` warns before dropping unfetched/unpushed commits. - security/workspace.md: the existing "Branch mode" stub (claiming the old `--branch` was a "workflow convenience, not a security boundary") is replaced with a "Clone mode" section that explicitly calls out the isolation guarantee — clone mode IS a security boundary, the host's `.git` cannot be touched. - security/_index.md: source-repository isolation is added to the five-layer model (was four). Wording aligned with isolation.md. Migration: callers that scripted `sbx create --branch=feature/x` now pass `--clone` and tell the agent to create the branch. This PR is an alternative to docker#25007, written against the post-rename CLI. Signed-off-by: Nicolas De loof <nicolas.deloof@gmail.com>
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… isolation Replaces the `--branch[=NAME]` documentation with `--clone` (boolean) on both `sbx create` and `sbx run`, matching the CLI rename in docker/sandboxes#3055. Clone mode is now strictly about running the agent on a private in-container `git clone --reference` of the host repository; no host-side branch is created on the user's behalf — the user instructs the agent to `git checkout -b ...` inside the sandbox if a dedicated working branch is needed. Key documentation changes: - usage.md: "Branch mode" section is renamed to "Clone mode" and rewritten end-to-end. Drops the `.sbx/<name>-worktrees/...` directory mention (no longer created), the host-side branch creation/checkout step, the `--branch=auto` flow, and the legacy "Multiple branches per sandbox" section. Adds: * an explicit note that clone mode is fixed at create time; * the forge-remote propagation behaviour (origin/upstream propagated from host into the in-container clone, local-path remotes skipped); * a Cleanup warning about lost in-container commits when running `sbx rm` (mirrors the runtime warning). - security/isolation.md: adds the "Source-repository isolation" section introduced in docker#25007. Same content, but uses `--clone` and "clone mode" terminology throughout, plus a clarifying note that `sbx rm` warns before dropping unfetched/unpushed commits. - security/workspace.md: the existing "Branch mode" stub (claiming the old `--branch` was a "workflow convenience, not a security boundary") is replaced with a "Clone mode" section that explicitly calls out the isolation guarantee — clone mode IS a security boundary, the host's `.git` cannot be touched. - security/_index.md: source-repository isolation is added to the five-layer model (was four). Wording aligned with isolation.md. Migration: callers that scripted `sbx create --branch=feature/x` now pass `--clone` and tell the agent to create the branch. This PR is an alternative to docker#25007, written against the post-rename CLI. Signed-off-by: Nicolas De loof <nicolas.deloof@gmail.com>
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Summary
Documents the branch-mode rework introduced in docker/sandboxes#2477, which replaces on-host Git worktrees with an in-container clone exposed over
git-daemon, and surfaces the new source-repository isolation guarantee.User-facing changes in
usage.md:sandbox-<name>Git remote that gets wired on the host.git worktree list,cd .sbx/...) with the simplergit fetch sandbox-<name>review flow..sbx/-directory and "multiple branches per sandbox" sections.--workspace-volume, host worktree).Security-model changes:
security/isolation.mdthat explains why the agent — even running unconstrained — cannot corrupt the host's.gitstate. The host source is bind-mounted read-only at/run/sandbox/source; the agent's clone is private (own index, own refs, own working tree) and shares only the immutable object database via.git/objects/info/alternates.security/_index.md.security/workspace.mdto correct the previous "branch mode is a workflow convenience, not a security boundary" caveat, which is no longer accurate after added compose file example in accordion #2477.The changes lean heavily on the threat-model framing the user asked for: the new design is not just ergonomic, it is the first time
--branchprovides a hard isolation boundary for the source repository.Dependency
This documentation describes behavior introduced by docker/sandboxes#2477, which is not yet merged at the time of opening this PR. Please hold this PR or land it on the next sandboxes release that ships #2477.
Test plan
usage.mdbranch-mode sectionsecurity/isolation.mdsource-repository-isolation sectionusage.md,security/workspace.md, andsecurity/isolation.md