agent-host: surface session git state via SessionState._meta

[roblourens]

The agent host process now computes per-session git state (branch, GitHub remote, ahead/behind, uncommitted changes) for sessions that have a working directory and publishes it through the protocol's per-session _meta. The Agents app reads it from SessionState._meta (not SessionSummary) and surfaces it via ISessionWorkspace, lighting up existing UI in the Changes view (e.g. ahead/behind indicators, branch info).

This is a narrower successor to #311815: just the metadata pipe, without skill syncing or toolbar button contributions. Those will be revisited separately.

Highlights

• New AgentHostGitService (server-side) computes git state by shelling out to git; refreshed on session open and after each turn.
• New SessionMetaChanged action propagates _meta deltas without a full list refresh.
• Client-side AgentHostSessionAdapter retains _project / _workingDirectory / _meta so the workspace observable can be rebuilt when only _meta changes.
• baseBranchProtected is computed client-side from git.branchProtection config, so the workspace shape no longer carries it as a field on ISessionRepository.
• update() only overwrites _meta when the source actually provides one (SessionSummary feeds have no _meta field), so the polling refresh path no longer clobbers good state pushed via SessionState.

(Written by Copilot)

[Copilot]

Pull request overview

This PR adds a per-session git-state “side channel” for agent-host sessions by computing git info in the agent-host process and publishing it via SessionState._meta, then adapting the Agents app/session providers to rebuild ISessionWorkspace when _meta changes so existing Changes UI can light up (branch/ahead-behind/uncommitted/GitHub remote).

Changes:

• Introduces SessionState._meta + SessionMetaChanged action in the AHP protocol and reducers, plus typed helpers (readSessionGitState, withSessionGitState) for the reserved git meta slot.
• Adds server-side git probing (AgentHostGitService.getSessionGitState) and hooks to refresh/publish git state on session open/restore and after each completed turn.
• Updates agent-host session adapters/providers to retain project/workingDirectory/meta and rebuild the workspace on _meta updates; updates UI logic to read git state from workspace repositories (vs session summary metadata).

Show a summary per file

File	Description
src/vs/workbench/contrib/chat/test/browser/agentSessions/agentHostChatContribution.test.ts	Adds regression test ensuring list metadata only includes working directory (git state no longer on summary).
src/vs/workbench/contrib/chat/browser/agentSessions/agentHost/agentHostSessionListController.ts	Stops emitting empty metadata; only includes remote host + workingDirectoryPath when present.
src/vs/sessions/services/sessions/common/session.ts	Extends ISessionRepository to carry git-related fields sourced from _meta.git.
src/vs/sessions/contrib/terminal/test/browser/sessionsTerminalContribution.test.ts	Updates tests for ISessionRepository shape change (removes explicit baseBranchProtected: undefined).
src/vs/sessions/contrib/remoteAgentHost/test/browser/remoteAgentHostSessionsProvider.test.ts	Stubs IConfigurationService required by provider changes.
src/vs/sessions/contrib/remoteAgentHost/browser/remoteAgentHostSessionsProvider.ts	Passes git state + branch protection patterns into workspace builder; injects configuration service.
src/vs/sessions/contrib/copilotChatSessions/browser/copilotChatSessionsProvider.ts	Stops expecting baseBranchProtected in metadata-derived repository objects.
src/vs/sessions/contrib/chat/test/browser/sessionsConfigurationService.test.ts	Updates test repository object to match optional baseBranchProtected.
src/vs/sessions/contrib/chat/test/browser/sessionWorkspacePicker.test.ts	Updates mock provider repository object for new ISessionRepository optional fields.
src/vs/sessions/contrib/changes/browser/changesViewModel.ts	Reads git state from workspace repositories for agent-host sessions; adjusts hasGitRepository derivation.
src/vs/sessions/contrib/agentHost/test/browser/localAgentHostSessionsProvider.test.ts	Stubs IConfigurationService required by provider changes.
src/vs/sessions/contrib/agentHost/browser/localAgentHostSessionsProvider.ts	Passes git state + branch protection patterns into workspace builder; injects configuration service.
src/vs/sessions/contrib/agentHost/browser/baseAgentHostSessionsProvider.ts	Retains _meta and rebuilds workspace on SessionMetaChanged via session-state subscription.
src/vs/sessions/common/agentHostSessionWorkspace.ts	Adds branch protection pattern helpers and maps _meta.git into ISessionRepository fields + workspace key.
src/vs/platform/agentHost/test/node/copilotGitProject.test.ts	Updates test git service stub for new getSessionGitState API.
src/vs/platform/agentHost/test/node/copilotAgent.test.ts	Updates test git service stub for new getSessionGitState API.
src/vs/platform/agentHost/test/node/agentSideEffects.test.ts	Updates tests for new onTurnComplete callback requirement.
src/vs/platform/agentHost/test/node/agentService.test.ts	Adds tests validating git state is attached to SessionState._meta.git when workingDirectory exists.
src/vs/platform/agentHost/test/node/agentHostGitService.test.ts	Adds unit tests for git parsing helpers (status v2, remotes, default branch ref).
src/vs/platform/agentHost/test/node/agentHostGitService.integrationTest.ts	Adds on-disk integration tests that spawn real git to validate computed session git state.
src/vs/platform/agentHost/node/agentSideEffects.ts	Calls onTurnComplete after idle to trigger post-turn git refresh.
src/vs/platform/agentHost/node/agentService.ts	Wires in git state refresh/publish on create/restore and post-turn; restores persisted _meta.
src/vs/platform/agentHost/node/agentHostStateManager.ts	Adds setSessionMeta dispatching SessionMetaChanged to update SessionState._meta.
src/vs/platform/agentHost/node/agentHostGitService.ts	Implements getSessionGitState by shelling out to git + adds parsing helpers.
src/vs/platform/agentHost/common/state/sessionState.ts	Defines SessionMeta, ISessionGitState, reserved git key, and helper read/write functions.
src/vs/platform/agentHost/common/state/protocol/version/registry.ts	Registers new actions as introduced in protocol v1.
src/vs/platform/agentHost/common/state/protocol/state.ts	Adds SessionState._meta and SessionSummary.activity; updates some schema JSDoc.
src/vs/platform/agentHost/common/state/protocol/reducers.ts	Handles SessionActivityChanged and SessionMetaChanged in reducer.
src/vs/platform/agentHost/common/state/protocol/actions.ts	Adds SessionActivityChangedAction and SessionMetaChangedAction.
src/vs/platform/agentHost/common/state/protocol/action-origin.generated.ts	Updates generated action unions and client-dispatchable map for new actions.
src/vs/platform/agentHost/common/state/protocol/.ahp-version	Syncs vendored protocol version to 84e5779.
src/vs/platform/agentHost/common/agentService.ts	Extends IAgentSessionMetadata with _meta?: SessionMeta.

Copilot's findings

Comments suppressed due to low confidence (2)

src/vs/platform/agentHost/node/agentService.ts:618

• Same as above: this comment says git state attaches under summary._meta.git, but the implementation uses SessionState._meta via setSessionMeta. Please update to avoid misleading future readers.

		// Lazily compute git state for sessions with a working directory;
		// attaches under `summary._meta.git` once ready.
		this._attachGitState(session, meta.workingDirectory);

src/vs/platform/agentHost/node/agentService.ts:343

• _attachGitState is fire-and-forget and can be triggered multiple times (session open + after each turn). Because results are applied asynchronously, a slower earlier probe can overwrite a newer git state snapshot and regress the UI. Consider tracking a per-session request counter / cancellation token and only applying the latest completed probe’s result.

	private _attachGitState(session: URI, workingDirectory: URI | undefined): void {
		if (!this._gitService || !workingDirectory) {
			return;
		}
		this._gitService.getSessionGitState(workingDirectory).then(
			gitState => {
				if (!gitState) {
					return;
				}
				const sessionKey = session.toString();
				const current = this._stateManager.getSessionState(sessionKey)?._meta;
				this._stateManager.setSessionMeta(sessionKey, withSessionGitState(current, gitState));
			},
			e => {
				this._logService.warn(`[AgentService] Failed to compute git state for ${session}`, e);
			},
		);

• Files reviewed: 32/32 changed files
• Comments generated: 4

[Copilot]

Copilot's findings

• Files reviewed: 31/31 changed files
• Comments generated: 3