Remove last vestiges of the master branch

Fixes #2372

Author: jimhester

README.md

@@ -2,7 +2,7 @@
 
 <!-- badges: start -->
 [![R-CMD-check](https://github.com/r-lib/devtools/workflows/R-CMD-check/badge.svg)](https://github.com/r-lib/devtools/actions)
-[![Codecov test coverage](https://codecov.io/gh/r-lib/devtools/branch/master/graph/badge.svg)](https://app.codecov.io/gh/r-lib/devtools?branch=master)
+[![Codecov test coverage](https://codecov.io/gh/r-lib/devtools/branch/main/graph/badge.svg)](https://app.codecov.io/gh/r-lib/devtools?branch=main)
 [![CRAN_Status_Badge](https://www.r-pkg.org/badges/version/devtools)](https://cran.r-project.org/package=devtools)
 <!-- badges: end -->
 
@@ -23,7 +23,7 @@ devtools::install_github("r-lib/devtools")
 
 ## Cheatsheet
 
-<a href="https://rawgit.com/rstudio/cheatsheets/master/package-development.pdf"><img src="https://raw.githubusercontent.com/batpigandme/cheatsheets/1c942c36846559b3e8efbd40d023bc351aeed6ba/pngs/thumbnails/package-development-thumbs.png" height="252"/></a>
+<a href="https://rawgit.com/rstudio/cheatsheets/main/package-development.pdf"><img src="https://raw.githubusercontent.com/batpigandme/cheatsheets/1c942c36846559b3e8efbd40d023bc351aeed6ba/pngs/thumbnails/package-development-thumbs.png" height="252"/></a>
 
 ## Usage
 
@@ -173,4 +173,4 @@ and visualization.
 
 ## Code of conduct
 
-Please note that the devtools project is released with a [Contributor Code of Conduct](https://github.com/r-lib/devtools/blob/master/.github/CODE_OF_CONDUCT.md). By contributing to this project, you agree to abide by its terms.
+Please note that the devtools project is released with a [Contributor Code of Conduct](https://github.com/r-lib/devtools/blob/main/.github/CODE_OF_CONDUCT.md). By contributing to this project, you agree to abide by its terms.

revdep/email.md

@@ -59,7 +59,7 @@ Because GitHub is the most commonly used unofficial package distribution in R, i
 Remotes: hadley/testthat
 ```
 
-You can also specify a specific hash, tag, or pull request (using the same syntax as `install_github()` if you want a particular commit. Otherwise the latest commit on the master branch is used.
+You can also specify a specific hash, tag, or pull request (using the same syntax as `install_github()` if you want a particular commit. Otherwise the latest commit on the HEAD of the branch is used.
 
 ```yaml
 Remotes: hadley/httr@v0.4,
@@ -92,10 +92,10 @@ Remotes: bitbucket::sulab/mygene.r@default, djnavarro/lsr
 Remotes: bioc::3.3/SummarizedExperiment#117513, bioc::release/Biobase
 
 # SVN
-Remotes: svn::https://github.com/hadley/stringr
+Remotes: svn::https://github.com/tidyverse/stringr
 
 # URL
-Remotes: url::https://github.com/hadley/stringr/archive/master.zip
+Remotes: url::https://github.com/tidyverse/stringr/archive/main.zip
 
 # Local
 Remotes: local::/pkgs/testthat