prototype

# git for-each-ref --sort="-committerdate" --format="%(refname)" refs/remotes | xargs --verbose -n 1 -i git --no-pager diff --name-only "HEAD...{}"
# git branch -r --no-merged | xargs -n 1 -i git --no-pager whatchanged --since=yesterday --source -1 "HEAD..{}" --

# Get files modified in branches updated today
rm -f thisids.txt thisfiles.txt thisbranch.txt
git for-each-ref --sort="-committerdate" --format="%(committerdate:short) %(refname)" refs/remotes | grep `date -d yesterday +%Y-%m-%d` | awk '{print $2}' | while read thisbranch; do
  git --no-pager diff --name-only master...$thisbranch -- *.java | while read thisfile; do
    thispatchid=`git diff master...$thisbranch -- $thisfile | git patch-id`
    echo $thisbranch $thispatchid $thisfile >> thisids.txt
    echo $thisfile >> thisfiles.txt
  done
  echo $thisbranch >> thisbranch.txt
done
if [ ! -e thisids.txt -o ! -e thisbranch.txt ]; then exit 0; fi # shortcircuit, nothing to do

sort thisfiles.txt | uniq > thisfiles.tmp
mv thisfiles.tmp thisfiles.txt 

# Get branches unmerged that are not stale
git branch -r --no-merged master | xargs -n 1 git log -1 --oneline --source --since=two.weeks.ago | awk '{print $2}' > thosebranches.txt

rm -rf branches
while read thatbranch; do
  git --no-pager diff --name-only master...$thatbranch -- *.java | while read thatfile; do
    mkdir -p branches/$thatfile
    echo $thatbranch >> branches/$thatfile/branches.txt
  done
done < thosebranches.txt

# Get files modified in unmerged branches
rm -f thoseids.txt
while read thisfile; do
  while read thatbranch; do
    thatpatchid=`git --no-pager diff master...$thatbranch -- $thisfile | git patch-id`
    if [ ! -z "$thatpatchid" ]; then
      echo $thisfile $thatpatchid $thatbranch >> thoseids.txt
    fi
  done < branches/$thisfile/branches.txt
done < thisfiles.txt

rm -rf refs
for i in `cat thisbranch.txt`; do 
  mkdir -p $i
done

awk '{
  branch=$1
  id=$2
  file=$4
  printf("grep \"%s\" thoseids.txt | grep -v %s | cut -d\" \" -f1,4 >> %s/conflicts.txt\n", file, id, branch)
}' thisids.txt | bash

find refs -type f -name conflicts.txt | xargs --verbose -n 1 cat

find refs -type f -name conflicts.txt -size 0 | xargs rm -f

rm -f emailbody.txt
cat thisbranch.txt | while read conflictbranch; do
  if [ -e $conflictbranch/conflicts.txt ]; then
    echo "==CONFLICTSET==" >> emailbody.txt
    echo `dirname ${conflictbranch#refs/remotes/*}` >> emailbody.txt
    echo "==SUMMARY==" >> emailbody.txt
    echo "in ${conflictbranch#refs/remotes/*} with " >> emailbody.txt
    cat $conflictbranch/conflicts.txt | awk '{print $2}' | sort | uniq >> emailbody.txt
    echo "==DETAILS==" >> emailbody.txt
    awk '{print $1}' $conflictbranch/conflicts.txt | sort | uniq | while read conflictfile; do
      grep $conflictfile $conflictbranch/conflicts.txt | head -20 | awk -v f=$conflictfile 'BEGIN {b=sprintf("%s:",f)} {b=sprintf("%s %s", b, $2)} END {print b}' >> emailbody.txt
      echo "--DETAIL--" >> emailbody.txt
    done
  fi
done
cat emailbody.txt