Split ServiceVerb repo-state check into intent-specific predicates

[tyrielv]

Problem

gvfs service --unmount-all intermittently fails with exit code 3 and Already unmounting, please wait, surfacing as the flaky functional test GVFS.FunctionalTests.Tests.MultiEnlistmentTests.ServiceVerbTests.ServiceCommandsWithNoRepos.

Root cause

The service verbs (--list-mounted, --mount-all, --unmount-all) iterate the service's global repo registry and used a single IsRepoMounted(repoRoot) helper. That helper returned true whenever the mount named pipe merely answered a GetStatus request — regardless of the actual MountState. StatusVerb reports success as long as it can connect, so a GVFS.Mount process in the transient Unmounting state (a concurrent or prior unmount still shutting it down) counts as "mounted."

--unmount-all therefore attempts to unmount a repo that is already on its way out, gets the transient Already unmounting response from the mount process, and treats it as a hard failure — even though the desired end state (repo unmounted) is already being reached.

Fix

Replace IsRepoMounted with three intent-specific predicates, all built on a TryGetRepoMountStatus primitive that reads the actual MountState:

Predicate	Meaning	Caller
IsRepoReady	MountState == Ready	--list-mounted
IsRepoAvailableToMount	no live mount process answering	--mount-all
IsRepoAvailableToUnmount	MountState ∈ {Ready, MountFailed}	--unmount-all

--unmount-all now skips repos that are Unmounting (already reaching the desired state) or Mounting (an unmount request would be rejected anyway), eliminating the spurious failure.

StatusVerb exposes the "Mount status: " output prefix as a shared constant so ServiceVerb recovers the MountState without re-implementing the pipe protocol (and without changing StatusVerb's worktree/enlistment resolution, so there's no behavior regression for worktree mounts).

Behavior changes

• --unmount-all: skips repos in Unmounting/Mounting instead of failing on them. (The fix.)
• --list-mounted: now reports only fully-Ready repos (previously also listed Mounting/Unmounting/MountFailed processes that happened to answer the pipe).
• --mount-all: unchanged — still mounts only when no live mount process is answering.

Testing

• Builds clean (dotnet build GVFS\GVFS\GVFS.csproj -c Debug, 0 warnings).
• Covered by the existing ServiceVerbTests functional suite (ServiceCommandsWithNoRepos, ServiceCommandsWithMultipleRepos, ServiceCommandsWithMountAndUnmount), whose expectations remain consistent with the new state-aware behavior. There is no unit-test seam for the service verbs (they require a live service pipe).

Related

This is the first of a set of fixes for the same flaky test. Two follow-ups are tracked separately: closing the mount-process lifecycle gap (a repo committed to unmounting still presents as a normal mounted repo to concurrent callers), and scoping the functional-test service registry so the global --mount-all/--unmount-all verbs can't reach across parallel fixtures.