Generate changelog from git history

changelog.sh

#!/bin/bash

CURRENTVER="v%build.number%" # This is teamcity replacement, could be param
LOGREGEX="[A-Z]+\-[0-9]+"

mkdir -p out
RESULTFILE=out/release-notes.txt
LASTTAG=$(git describe --tags --abbrev=0)
SINCE="v2.0.0" #"${SINCE:-${LASTTAG}}"
mapfile -t tags < <( git tag --contains $SINCE )
LAST="HEAD"
LASTTEXT=$CURRENTVER
STARTPOS=1
if [ "${LASTTAG}" = "${LASTTEXT}" ]; then
  echo "Build number is same as last tag so we skip ther first entry"
  STARTPOS=2
fi
echo "Generating change log since ${SINCE}, last tag was ${LASTTAG}"
echo "# Changelog" > "$RESULTFILE"
for (( idx=${#tags[@]}-$STARTPOS ; idx>=0 ; idx-- )) ;
do
  tag="${tags[idx]}"
  echo "Tag ${tag}"
  echo "" >> "$RESULTFILE"
  echo "## ${LASTTEXT}" >> "$RESULTFILE"
  echo "" >> "$RESULTFILE"

  git log "${tag}..${LAST}" --pretty=format:"%s %b" \
    | grep -E $LOGREGEX \
    | sed -n -r "s/^Merge pull request #[0-9]+ from [a-zA-Z0-9\/\-\-]* //p" \
    >> "$RESULTFILE"

  LAST="${tag}"
  LASTTEXT="${tag}"
done

echo "" >> "$RESULTFILE"
echo "## ${SINCE}" >> "$RESULTFILE"
echo "(omitted)" >> "$RESULTFILE"

echo ""
echo "Done. The result is:"
echo ""
cat ${RESULTFILE}