Add() with no ForPath/All/UpdateTrackedOnly reports success having staged nothing, and All().UpdateTrackedOnly() reaches git as a fatal usage error #172

What's wrong

repository.Add().ExecuteAsync() with nothing configured runs git … add with no pathspec. Git prints Nothing specified, nothing added. and exits 0, so the builder returns a GitCompleted as if staging had worked.

GitAddBuilder.AppendVerbArguments (GitIntegration/Builders/GitAddBuilder.cs:69-97) emits add, then --all/--update if set, then operands if any. Nothing checks that there is anything to stage.

The opposite mistake isn't checked either. Add().All().UpdateTrackedOnly() emits add --all --update, which git rejects with fatal: options '-A' and '-u' cannot be used together (exit 128). The caller gets a generic GitCommandException with no hint that two fluent calls conflict.

Verified with git 2.43:

$ git add; echo $?
Nothing specified, nothing added.
hint: Maybe you wanted to say 'git add .'?
0
$ git add --all --update; echo $?
fatal: options '-A' and '-u' cannot be used together
128

Why it matters

A caller who forgets .All() or .ForPath(...) gets a success result. The following Commit(...) then either throws GitNothingToCommitException or commits only what was staged earlier, far from the real mistake.

Other builders already refuse impossible configurations before spawning git:

• GitFetchBuilder rejects AllRemotes() + FromRemote(...) (GitFetchBuilder.cs:21-38).
• GitCheckoutBuilder rejects CreatingBranch() + Detach() (GitCheckoutBuilder does not reject CreatingBranch() + Detach(), which git refuses at runtime #91).

Suggested fix / acceptance criteria

• An Add() builder with no paths and neither All() nor UpdateTrackedOnly() throws InvalidOperationException before any process starts, and TryExecuteAsync behaves the same, matching the Fetch guard.
• All() combined with UpdateTrackedOnly() is either refused the same way, or documented as last-call-wins like IGitBranchListBuilder.LocalOnly/RemoteOnly. Git's fatal error should not be the only signal.
• If the check goes in BuildArguments() as Fetch's does, update GitRepositoryMutatingVerbTests.EveryMutatingVerbIsScopedToTheRepositoryPath (GitIntegration.Test/GitRepositoryMutatingVerbTests.cs:28). It calls repository.Add().BuildArguments() bare, so it needs e.g. .All().
• Builder tests cover both refusals, and the existing vectors for ForPath, All and UpdateTrackedOnly used alone are kept.