git-navigation.sh

# Git Navigation
# 
# By Hannes Tydén <hannes@tyden.name> @pht
#
# Navigate backwards and forwards in your Git history.
# 
# Inspired by https://twitter.com/avdi/status/292057753088827392
#
# Tested on
# zsh 5.0.2 (x86_64-apple-darwin12.2.1)
# git version 1.8.1

git-backward() {
  git checkout HEAD~
}

git-forward () {
  children=$(git-children)
  child_count=$(echo $children | grep . | wc -l | git-support-trim)
  if [[ $child_count -eq 1 ]]
  then
    git checkout $children
  else
    echo "Cannot go forward"
    echo "$(git-sha) has $child_count children"
    if [[ $child_count -eq 0 ]]
    then
      tips=$(git-branch-leaf-shas | grep '^\*' | sed 's/^\* *//')
      if [[ $(echo $tips | grep . | wc -l | sed 's/ *//') -ne 0 ]]
      then
        echo Also HEAD is the leaf of
        echo $tips
      fi
    else
      for child in $(echo $children)
      do
        echo "$child ($(git-status-in-branches $child | git-support-collapse | git-support-trim))"
      done
      echo
      echo "    git checkout <sha> to continue ..."
      echo
    fi
  fi
}

git-sha () {
  git log --format=format:%H --max-count 1 $@
}
git-children () {
  # http://stackoverflow.com/questions/1761825/referencing-the-child-of-a-commit-in-git
  treeish=$1
  git rev-list --parents --all $treeish | grep " $(git-sha $treeish)" | cut -d ' ' -f 1
}
git-branch-leaf-shas () {
  git branch -v --no-abbrev | grep -v '(no branch)' | sed -E 's/^[* ] ([^[:space:]]+)[[:space:]]+([[:alnum:]]+).*/\2 \1/'
}
git-leaf-in-branches () {
  sha=$(git-sha $1)
  git-branch-leaf-shas | grep $sha | sed "s/${sha}[[:space:]]*//"
}
git-status-in-branches () {
  # * infront of the branch name indicates that the sha is the leaf of the branch
  sha=$(git-sha $1)
  comm -1 <(git-leaf-in-branches $sha) <(git branch --contains $sha | grep -v '(no branch)' | sed 's/[[:space:]]*//') | sed -E 's/^[[:space:]]+/*/'
}

git-support-trim () {
  sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//'
}
git-support-collapse () {
  tr '\n' ' ' | sed -E 's/[[:space:]]+/ /'
}