TTreeViewer save session absolute path

[ferdymercury]

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Description

When I open a TFile with a classic TBrowser, right click on a Ttree, StartViewer, then File Save source, /tmp/session.C, and then File load Session, and I select that file, I get an error.
Reason is that the created macro contains the slash verbatim as the name of the main function, rather than stripping the part of the path that is the basedir.

Reproducer

See above

ROOT version

6.32.04

Installation method

Binary

Operating system

Ubuntu 24

Additional context

std filesystem might help here