Method _getVersionSign

src/data/helper/sourceManager.ts:179–181

* For detecting whether the upstream source is dirty, so that * the local cached source (in `_sourceList`) should be discarded.

()

     * the local cached source (in `_sourceList`) should be discarded.
     */
    private _getVersionSign(): string {
        return this._sourceHost.uid + '_' + this._versionSignBase;
    }

    /**
     * Always return a source instance. Otherwise throw error.