src/utils/working.js
function getMergedFileSet(workingState) {
    return Immutable.Set.fromKeys(
        getMergedTreeEntries(workingState).filter(
            treeEntry => treeEntry.getType() === TreeEntry.TYPES.BLOB
        )
    );
}
function getMergedFileSet(workingState) {
    return Immutable.Set.fromKeys(
        getMergedTreeEntries(workingState).filter(
            treeEntry => treeEntry.getType() === TreeEntry.TYPES.BLOB
        )
    );
}
Returns a Seq of tree mixing changes and the fetched tree
@param {WorkingState}
@return {Set<Path>}