Add archive.rds and expand package path to allow archived versions of R packages

[craddm]

This allows the R remotes package to download and install older versions of R packages. It permits required metadata to be downloaded and modifies the content selector for each package to allow archived package versions to be found.

Closes #57

[JimMadge]

@craddm could you give me a R command/script to install a package from the archive so I can test this?

[craddm]

@craddm could you give me a R command/script to install a package from the archive so I can test this?

remotes::install_version("data.table", version = "1.13.0") should do - slightly older version, and data.table is on our allow list.

(you will need to make sure remotes is installed first, install.packages("remotes")

[JimMadge]

Can you do the same with install.packages?

[craddm]

Can you do the same with install.packages?

You'd have to generate the correct URL, e.g.

packageurl <- "http://cran.r-project.org/src/contrib/Archive/ggplot2/ggplot2_0.9.1.tar.gz"
install.packages(packageurl, repos=NULL, type="source")

I suppose with the nexus repo setup you could do something like this for an older version of a package

packagename <- "data.table"
version <- "1.13.0"
packageurl <- paste0(contrib.url(getOption("repos")), "/Archive/", packagename, "/", packagename, "_", version, ".tar.gz")
install.packages(packageurl, repos=NULL, type="source")

[JimMadge]

Do you think remotes is common/important enough to support?

I thought the attitude of CRAN was along the lines of "Use only the latest set of all packages, that is what we guarantee to be compatible".

[craddm]

Do you think remotes is common/important enough to support?

I thought the attitude of CRAN was along the lines of "Use only the latest set of all packages, that is what we guarantee to be compatible".

If we're not using the latest R, which we're not, we'll need to support installing older package versions. Also there may be good reason to use specific package versions (e.g. replicating an earlier analysis)