Strip URL parameters for local filename

[jeroen]

Currently download.packages() copies the full File field from the URL in PACKAGES, including http parameters, as the local filename. So for example, if the PACKAGES file contains

Package: jsonlite
Version: 2.0.0
File: jsonlite_2.0.0.tar.gz?somekey=79fad1b6092c1d1cc71e096d02cbc7618837fda1f90b61443f09adc25caab095
...

Then the file is saved locally not as jsonlite_2.0.0.tar.gz but as the full url including the ? and = characters which are not allowed in filenames on some platforms.

To reproduce this I created a testing repo:

available.packages(repos = 'https://jeroen.github.io/testrepo/')
download.packages('jsonlite', '.', repos = 'https://jeroen.github.io/testrepo/')

The above patch makes the download behavior of R correspond to browsers, which is to remove the http-query part from the url when saving a file locally.