[Feature] A branch renaming function?

[Moelf]

Symbol("STDMTruthTausAuxDyn.classifierParticleOrigin") is crazy branch name and it includes a dot...

[aminnj]

Ttrees have a SetAlias function that lets it map a convenient alias to a branch expression and I think these are stored in fAliases. I agree this could be nice. Especially a lazy expression evaluator :) like a pt column lazily constructed from px py columns on the fly.

[Moelf]

one thing I want is normalizenames like in CSV.jl, which would convert dot to _. As for renaming, DataFrames.jl uses rename!()

[Moelf]

https://root.cern.ch/doc/master/classTTree.html#a7c505db0d8ed56b5581e683375eb78e1

Alias allows formula,

tree->SetAlias("x1","(tdc1[1]-tdc1[0])/49");

I think the natural translation to Julia would be:

setalias!(tree, :tdc1 => ( x-> (x[2]-x[1])/49) => :x1)

taking inspiration from https://dataframes.juliadata.org/stable/lib/functions/#DataFrames.combine

but too convoluted, don't feel like useful enough LOL

[Moelf]

implemented in #225 with a slightly different interface (rename at creation time)