Using git bisect to find the original commit that a piece of code/text entered the repo. Need this because many times you want to trace back when it was added, but when running a git show/blame you end up finding commits that just move that chuck around in the file/to different files etc.

git-find-original.sh

# USAGE:
# reason for this is because sometimes you want to know when the originating code/comment/whatever was brought into the repo
# but you end up following a trace of lots of commits that just moved around the original chunk of code.
# this uses git bisect to trace back to the original commit that has this text in the repo.
# depends on ack, but you could easily change this to use `grep -r`
#
# $ git-find-original "some search string that you want to find the original commit that had this exact text"

match_arg="$@"

continue_bisect() {
  previous_commit=$1
  current_commit=$(git rev-list HEAD |head -1)

  if [ "$previous_commit" = "$current_commit" ]; then
    # we've reached the commit we want
    echo
    echo "============================================="
    echo "run a git show or what have you. you're here."
    echo "============================================="
    echo
    return
  fi

  ack "$match_arg"
  ret=$?
  # successful ack, we want to mark as bad, continue until we do
  # not find any match, and then mark it good
  if [ $ret -eq 0 ]; then
    git bisect bad
    continue_bisect $current_commit
  else
    git bisect good
    continue_bisect $current_commit
  fi
}

initial_commit=$(git rev-list HEAD | tail -n 1)

git bisect start
git bisect good $initial_commit
continue_bisect

Actually looks like this is the same thing:

git log -S "string to find" --oneline | tail -n 1

Thanks to https://twitter.com/michaelfairley

Looks like the git bisect approach might be faster than git log -S though. Could use more benchmarks, but does anyone really care? Was for me, but it does depend on git commit history length for the repo.