TChain::Add and TChain::AddFile are broken when the provided URL contains double slashes in the path component, eg root://some.domain/path/to//file.root.
Minimal repro case:
This yields to:
Notice how the path is truncated (and hence trying to use the TChain doesn't work). For comparison, in ROOT 6.12 (LCG 93) the path is added correctly:
So this is a regression between 6.12 and 6.14.
This is caused by this code in TChain.cxx: the variable fn contains the normalized path (path/to/file.root in my example). Since the normalized path isn't present in filename, filename.Index(fn) returns -1 and things break down.
An obvious workaround is to always normalize the URL before adding files.