doc: clarify location of rPackages overrides

Detail the location of rPackage overrides and how broken
builds should be addressed.

Changed files
+13 -1
doc
languages-frameworks
+13 -1
doc/languages-frameworks/r.section.md
···
## Updating the package set {#updating-the-package-set}
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There is a script and associated environment for regenerating the package
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sets and synchronising the rPackages tree to the current CRAN and matching
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BIOC release. These scripts are found in the `pkgs/development/r-modules`
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directory and executed as follows:
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```bash
nix-shell generate-shell.nix
···
mv bioc-experiment-packages.nix.new bioc-experiment-packages.nix
```
-
`generate-r-packages.R <repo>` reads `<repo>-packages.nix`, therefor the renaming.
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`generate-r-packages.R <repo>` reads `<repo>-packages.nix`, therefore
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the renaming.
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Some packages require overrides to specify external dependencies or other
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patches and special requirements. These overrides are specified in the
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`pkgs/development/r-modules/default.nix` file. As the `*-packages.nix`
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contents are automatically generated it should not be edited and broken
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builds should be addressed using overrides.