Adding a custom kdiff3 mergetool

mitm_kdiff3.sh

#!/usr/bin/env bash

# Add to .gitconfig
# [merge]
#	tool = mitmkdiff3
# [mergetool.mitmkdiff3]
#	cmd = mitm_kdiff3 "$LOCAL" "$REMOTE" "$MERGED" "$BASE"

: ${MERGE_TOOLS_DIR=$(git --exec-path)/mergetools}

blob_to_commit()
{
  git log --all --pretty=format:'%T %H' | while read tree commit; do 
    if git ls-tree -r $tree | grep -q $1; then 
      echo $commit
      break
    fi
  done
}

LOCAL=$1
REMOTE=$2
MERGED=$3
BASE=$4

blob_to_commit2()
{
  git log --all --pretty=format:'%T %H' | while read tree commit; do 
    if git ls-tree -r $tree | grep -q $1; then 
      echo $commit
    fi
  done
}


local_sha1=$(git ls-files -u -- "$MERGED" | awk '{if ($3==2) print $2;}')
remote_sha1=$(git ls-files -u -- "$MERGED" | awk '{if ($3==3) print $2;}')
base_sha1=$(git ls-files -u -- "$MERGED" | awk '{if ($3==1) print $2;}')

local_commit_sha1=$(blob_to_commit $local_sha1)
remote_commit_sha1=$(blob_to_commit $remote_sha1)

if [ "${base_sha1}" != "" ]; then
  base_commit_sha1=$(blob_to_commit $base_sha1)
  exec kdiff3 --auto \
    --L1 "$MERGED (Base) ${base_commit_sha1}" \
    --L2 "$MERGED (Local) ${local_commit_sha1}" \
    --L3 "$MERGED (Remote) ${remote_commit_sha1}" \
    -o "$MERGED" "$BASE" "$LOCAL" "$REMOTE" \
  >/dev/null 2>&1
else
  exec kdiff3 --auto \
    --L1 "$MERGED (Local) ${local_commit_sha1}" \
    --L2 "$MERGED (Remote) ${remote_commit_sha1}" \
    -o "$MERGED" "$LOCAL" "$REMOTE" \
  >/dev/null 2>&1
fi