git-lye.sh

# git lye

# An attempt to make rebasing easy, by draining unnessarcy commit noise.
# No warranty, use at own risk.

# Author Hannes Tydén <hannes@tyden.name>
# Contributor Tobias Schmidt <ts@soundcloud.com>

# TODO
# - Don't sign off all commits are by current user.

# Name of the source branch containing the changes.

if [ $# -eq 0 ]; then
  echo "usage: git lye <source>"
else
  SOURCE=$1

  # Format of the change commits in the drained commit.
  FORMAT="# Commmit %H%n# Author: %aN <%ae>%n# Date: %ai%n* %B"

  # Temp files.
  GIT_LYE_LOG=/tmp/git-lye-log
  GIT_LYE_AUTHORS=/tmp/git-lye-authors

  # Number of commits in target branch not included in source.
  # Includes merge commits.
  COMMITS=$(git rev-list $SOURCE.. | wc -l | sed -e 's/[[:space:]]//g')
  R_COMMITS=$(git rev-list ..$SOURCE | wc -l | sed -e 's/[[:space:]]//g')

  if [ $COMMITS -eq 0 ]; then
    COMMITER=`git config --get user.email`
    printf "# Draining $R_COMMITS commits from branch '$SOURCE'\n" >> $GIT_LYE_LOG
    # good commit message: http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html
    printf "# Please provide a descriptive commit message:\n" >> $GIT_LYE_LOG
    printf "$SOURCE\n\n" >> $GIT_LYE_LOG
    # Merge commit messages are usually not interesting.
    git log ..$SOURCE --reverse --no-merges -z --format=format:"$FORMAT" >> $GIT_LYE_LOG
    # Append
    printf "# End of commits.\n" >> $GIT_LYE_LOG
    # List of unique authors, last commiter first.
    git log ..$SOURCE --no-merges --format='%aN <%ae>' | cat - | awk '{count[$0]++}END{for(j in count) print j,"("count[j]" commits)"}' > $GIT_LYE_AUTHORS
    # Last author will be author of drained commit.
    GIT_AUTHOR=$(head -n 1 $GIT_LYE_AUTHORS)
    # Date will be date of last commit
    AUTHOR_DATE=$(git log $SOURCE -n1 --format=format:%ad)
    AUTHORS=$(cat $GIT_LYE_AUTHORS | wc -l | sed -e 's/[[:space:]]//g')
    # If there are more then 1 author we list them all at the bottom.
    if [ $AUTHORS -gt 1 ]; then
      # Prepend
      printf "\n$AUTHORS authors:\n" | cat - $GIT_LYE_AUTHORS | tee $GIT_LYE_AUTHORS > /dev/null
    else
      # If the current user is not in the list of commiters he signs this off.
      if [ -z "$(grep $COMMITER $GIT_LYE_AUTHORS)" ]; then
        SIGNOFF="-s"
      fi
      # Clear author list
      ! > $GIT_LYE_AUTHORS
    fi

    # Create diff and apply
    # git diff ..$SOURCE | git apply --whitespace=nowarn
    # To support binary changes
    git diff ..$SOURCE --full-index --binary | git apply --whitespace=nowarn
    # Add files created through the apply
    git add .
    # Remove files deleted through the apply
    DELETED_FILES=$(git ls-files -d)
    if [ -n "$DELETED_FILES" ]; then
      git rm $DELETED_FILES
    fi
    # Commit with template message
    git commit "--author=$GIT_AUTHOR" "--date=$AUTHOR_DATE" -e $SIGNOFF -m "$(cat $GIT_LYE_LOG $GIT_LYE_AUTHORS)"
    if [ $? -eq 0 ]; then
      echo "$R_COMMITS commit(s) drained."
    else
      git reset --hard
      echo "Draining aborted."
    fi
    # Clean up
    rm $GIT_LYE_LOG $GIT_LYE_AUTHORS
  else
    echo "There are $COMMITS commit(s) in the current branch that prevents draining."
    echo "Please merge these into $SOURCE and try again."
    echo ""
    git log $SOURCE.. --format=oneline
  fi
fi