Git Log script using r, a spin-off from watching https://www.youtube.com/watch?v=CB9p8n3gugM, no libs allowed. see also: https://gist.github.com/neerajt/4f04f3d7dd93b51dabbcac5e4a0b0456

git-logger.r

GIT_PATH <- '.git'
PARENT_SEP <- 'parent '

get_log <- function() {
  current_hash <- get_current_hash()

  current_commit <- get_commit(current_hash)

  all_commits <- c(format_commit(current_hash, current_commit))

  while(has_parent(current_commit)){
    current_hash <- get_parent_of_commit(current_commit)

    current_commit <- get_commit(current_hash)

    all_commits <- append(all_commits, format_commit(current_hash, current_commit))
  }

  print(cat(paste(all_commits, collapse='\n')))
}

format_commit <- function(hash, commit){

  commit_keeps <- !sapply(commit, is_parent_or_tree)

  return(append(c('', paste0('\033[1;37m','commit ', hash, '\033[0m')), commit[commit_keeps]))
}

has_parent <- function(commit){
  return(any(sapply(commit, is_parent)))
}

is_parent_or_tree <- function(commitLine){
  return(is_tree(commitLine) | is_parent(commitLine))
}

is_tree <- function(commitLine){
  return(regexpr('tree ', commitLine)[1] == 1)
}

is_parent <- function(commitLine){
  return(regexpr(PARENT_SEP, commitLine)[1] == 1)
}

get_parent_of_commit <- function(commit){
  return(gsub(PARENT_SEP, '', commit[2]))
}

get_commit <- function(hash){
  GIT_COMMAND <- 'git cat-file -p '

  return(system(paste0(GIT_COMMAND, hash), intern=TRUE))
}

get_current_hash <- function() {
  REF_SEP <- 'ref: '

  ref <- readLines(get_git_dir('HEAD'))

  ref_directory <- gsub(REF_SEP, '', ref)

  return(readLines(get_git_dir(ref_directory)))
}

get_git_dir <- function(subdir) {
  return(paste0(GIT_PATH, '/', subdir))
}

get_log()