last_release_in_majors.R

#' Get a list of git tags
#'
#' @param pattern 
#'
#' @return
#'
#' @examples
get_tags <- function(pattern=NULL) {
  all_tags <- system2("git", c("tag", "--sort=taggerdate"), stdout = TRUE)
  
  if (is.null(pattern)) {
    return(all_tags)
  }
  
  all_tags[grepl(tag_pattern, all_tags, perl = TRUE)]
}

#' Get the latest release within a major series
#'
#' @param tags 
#' @param major 
#' @param tag_prefix 
#'
#' @return
#'
#' @examples
latest_release_for_major <- function(tags, major, tag_prefix) {
  releases_in_major <- tags[grep(paste0(tag_prefix, major), tags)]
  sub(tag_prefix, "", releases_in_major[length(releases_in_major)])
}

#' Get the major version from a git tag
#'
#' @param tag 
#' @param tag_prefix 
#'
#' @return
#'
#' @examples
major_from_tag <- function(tag, tag_prefix) {
  tag_version <- package_version(sub(tag_prefix, "", tag))
  tag_version$major
}

#' Get the latest release in one or more major release series
#'
#' @param n 
#' @param tag_prefix 
#' @param tag_pattern 
#'
#' @return
#'
#' @examples
last_n_releases_for_majors <- function(n, 
                                       tag_prefix="apache-arrow-", 
                                       tag_pattern="apache-arrow-[\\d\\.]+$") {
  tags <- get_tags(tag_pattern)
  
  latest_tag <- tags[length(tags)]
  latest_major <- major_from_tag(latest_tag, tag_prefix)
  target_majors <- rev(latest_major - 0:2)
  
  vapply(
    target_majors, 
    function(major) {
      latest_release_for_major(tags, major, tag_prefix) 
    },
    ""
  )
}

last_n_releases_for_majors(3)