DXR fails to index files tracked by git when www_root is set

[hujiajie]

DXR would fail at

dxr/dxr/plugins/core.py

Line 524 in addafaf

[('permalink', 'Permalink', url_for('.rev',

.
It seems to work by changing

dxr/dxr/build.py

Line 568 in addafaf

with make_app(tree.config).test_request_context():

to

with make_app(tree.config).test_request_context(tree.config.www_root + '/'):

but I'm new to Flask, so not sure if the fix is right.