Use expensive timeout for git checkout

This can be slow on large repos, but also often seems to be particularly
slow on windows. Adding --progress would help with this, but we probably
need to sniff versions for that.

Fixes #948

internal/gps/vcs_repo.go

@@ -98,7 +98,7 @@ func (r *gitRepo) fetch(ctx context.Context) error {
 }
 
 func (r *gitRepo) updateVersion(ctx context.Context, v string) error {
-	out, err := runFromRepoDir(ctx, r, defaultCmdTimeout, "git", "checkout", v)
+	out, err := runFromRepoDir(ctx, r, expensiveCmdTimeout, "git", "checkout", v)
 	if err != nil {
 		return newVcsLocalErrorOr("Unable to update checked out version", err, string(out))
 	}