gk.sh

# GitKit
## Experimental git branch management tool

function gk(){
  if [ $# -eq 0 ]; then
    echo "Usage: gk <command> [args]"
    echo "Commands:"
    echo "  branch <branch> - create a new branch off the current branch"
    echo "  parent [branch] - get the parent of the current branch or the given branch"
    echo "  children [branch] - get the children of the current branch or the given branch"
    echo "  upchain [branch] - list the chain of branches from the current branch or the given branch"
    echo "  downchain [branch] - list the chain of branches from the current branch or the given branch"
    echo "  chain [branch] - list both upchain and downchain in order"
    echo "  evolve - rebase all children on top of the current branch, recursively"
    echo "  up - move one branch up the chain"
    echo "  down - move one branch down the chain"
    echo "  setparent <parent> - set the parent of the current branch"
    echo "  markmerged - mark the current branch as merged"
    return 1
  fi
  local command=gk_$1
  shift
  if ! git rev-parse --is-inside-work-tree > /dev/null 2>&1; then
    echo "ERROR: Not in a git repository"
    return 1
  fi
  $command $@
}


function gk_branch(){
  if [ $# -eq 0 ]; then
    echo "Usage: gk branch <branch>"
    return 1
  fi
  local dependent=$1
  local base=$(git rev-parse --abbrev-ref HEAD)

  # If branch has already been created, fail
  if git show-ref --verify --quiet refs/heads/$dependent; then
    echo "Branch $dependent already exists"
    return 1
  fi

  git checkout -b $dependent
  git config branch.$dependent.description "$base"
}

function gk_parent(){
  local branch
  if [ $# -eq 0 ]; then
    branch=$(git rev-parse --abbrev-ref HEAD)
  else
    branch=$1
  fi
  git config branch.$branch.description
}

function gk_children(){
  local base_branch
  if [ $# -eq 0 ]; then
    base_branch=$(git rev-parse --abbrev-ref HEAD)
  else
    base_branch=$1
  fi
  git for-each-ref --format='%(refname:short)' refs/heads | while read b; do
    if [ "$(gk_parent $b)" = "$base_branch" ]; then
      echo $b
    fi
  done
}

function listchain_helper(){
  local branch=$1
  echo $branch
  local parent=$(gk_parent $branch)
  if [ -n "$parent" ]; then
    listchain_helper $parent
  fi
}

function gk_upchain(){
  local branch
  if [ $# -eq 0 ]; then
    branch=$(git rev-parse --abbrev-ref HEAD)
  else
    branch=$1
  fi
  listchain_helper $branch
  echo "-- end of chain --"
}

function gk_downchain(){
  local branch
  if [ $# -eq 0 ]; then
    branch=$(git rev-parse --abbrev-ref HEAD)
  else
    branch=$1
  fi
  local children=$(gk_children $branch)

  # if multiple children, print out a special message
  echo $branch
  if [ $(echo $children | wc -w) -gk 1 ]; then
    echo "[multiple children]"
  elif [ -n "$children" ]; then
    gk_downchain $children
  else 
    echo "-- end of chain --"
  fi
}

function gk_chain(){
  local branch
  if [ $# -eq 0 ]; then
    branch=$(git rev-parse --abbrev-ref HEAD)
  else
    branch=$1
  fi
  # reverse the order of the upchain, appending a star as the last character on the last line
  gk_upchain $branch | tac | sed '$ s/$/*/'
  gk_downchain $branch | tail -n +2
}

function gk_evolve(){
  # rebase all children on top of the current branch, recursively
  local branch=$(git rev-parse --abbrev-ref HEAD)
  local children=$(gk_children $branch)
  for child in $children; do
    echo "Rebasing $child on $branch"
    git checkout $child
    git rebase $branch
    gk_evolve
  done
  git checkout $branch
}

function gk_up(){
  # Move one branch up the chain
  local branch=$(git rev-parse --abbrev-ref HEAD)
  local parent=$(gk_parent $branch)
  if [ -n "$parent" ]; then
    git checkout $parent
  else 
    echo "No parent branch"
  fi
}

function gk_down(){
  # Move one branch down the chain
  local branch=$(git rev-parse --abbrev-ref HEAD)
  local children=$(gk_children $branch)
  # If multiple children, fail
  if [ $(echo $children | wc -w) -gt 1 ]; then  
    echo "Multiple children branches"
    return 1
  fi
  if [ -n "$children" ]; then
    git checkout $children
  else 
    echo "No child branch"
  fi
}

function gk_setparent(){
  # Set the parent of the current branch
  local branch=$(git rev-parse --abbrev-ref HEAD)
  local parent=$1
  if [ -z "$parent" ]; then
    echo "Usage: gk setparent <parent>"
    return 1
  fi
  git config branch.$branch.description $parent
}

function gk_markmerged(){
  # Mark the current branch as merged

  local branch=$(git rev-parse --abbrev-ref HEAD)
  # If git disagrees that it's merged, fail
  if ! git branch --merged main | grep -q $branch; then
    echo "Branch $branch is not merged"
    return 1
  fi
  local children=$(gk_children $branch)
  for child in $children; do
    git checkout $child
    gk_setparent main
  done
  git checkout $branch
}