code that can revise DESCRIPTION to add a package that is needed, bump version, and take care of git operations

revise_source.R

#' @param dry_run logical(1) if TRUE, just return revised DESCRIPTION
#' @return `desc::description` instance; will write revised DESCRIPTION to `path` if `dry_run` FALSE.
#' @note Bumps third component of version tag
#' @export
revise_desc = function(path, type="Suggests", to_add="rmarkdown", dry_run=TRUE) {
   stopifnot(is.atomic(to_add) && length(to_add)==1)
   init = desc::description$new(path)
   deps = init$get_deps()
   if (to_add %in% deps$package) stop("already depended upon")
   init = init$set_dep(type=type, package=to_add)
   init$bump_version(3)
   if (!dry_run) init$write(path)
   init
}

#' use gert and desc to revise DESCRIPTION to add a single package to a DESCRIPTION dependencies field
#' @param pkgname package for which DESCRIPTION is to be revised
#' @param to_add character(1) package name to add to DESCRIPTION field
#' @param field character(1) a DESCRIPTION field
#' @param msg character(1) commit message, edit
#' @param branch character(1) defaults to "master"
#' @param dry_run logical(1) if TRUE, just return revised DESCRIPTION
#' @param where character(1) where to carry out revision, defaults to `tempdir()`
#' @export
revise_source = function(pkgname, to_add="rmarkdown", field="Suggests", msg="add rmarkdown to Suggests",
    branch="master", dry_run=TRUE, where=tempdir()) {
   curd = getwd()
   td = where
   on.exit(setwd(curd))
   setwd(td)
   if (!dir.exists(pkgname)) gert::git_clone(
         sprintf("[email protected]:packages/%s", pkgname))
   setwd(pkgname)
   gert::git_branch_checkout(branch)
   rd = revise_desc("DESCRIPTION", to_add=to_add, type=field, dry_run=dry_run) 
   if (dry_run) return(rd)
   gert::git_add("DESCRIPTION")
   gert::git_commit(msg)
   gert::git_push("origin")
}