This is a quick shell script to generate an changelog entry.

create_changelog_entry.sh

#!/bin/bash

# This should be a perl/ruby/python/go program,
# but for now it's going to be in Bash.

DIRNAME=$( dirname $0 )

## First some configuration
if [[ -z "$MASTER_BRANCH" ]]; then
    MASTER_BRANCH=master
fi

if [[ -z "$CONTROL_FILE" ]]; then
    CONTROL_FILE="$DIRNAME/control"
fi

if [[ -z "$CHANGELOG_FILE" ]]; then
    CHANGELOG_FILE="$DIRNAME/changelog"
fi


#-------------------------------------------------------------------------------
#  Script variables
#-------------------------------------------------------------------------------
touch $CHANGELOG_FILE

if [ -z "$PACKAGE_URGENCY" ]; then
    PACKAGE_URGENCY='low'
fi

if [ -z "$PACKAGE_STABLE" ]; then
    PACKAGE_STABLE='unstable'
fi

PACKAGE_NAME=$(
    grep 'Package:' ${CONTROL_FILE} \
    | cut -d ':' -f 2               \
    | tr -d ' '
)
VERSION_NUMBER=$(
    grep ${PACKAGE_NAME} ${CHANGELOG_FILE} \
    | head -n 1                            \
    | perl -pe '/\(([[:alnum:].-]+)\)/; $_=$1'
)

if [[ ! -z "${SNAPSHOT_NAME}" ]]; then
    #echo "Snapshot Name provided: $SNAPSHOT_NAME"
    IS_GOOD=$(perl -E "say(('${SNAPSHOT_NAME}' =~/[^[:alnum:].-]/g)?'NO':'YES')")
    if [[ "NO" ==  "$IS_GOOD" ]]; then
        cat <<ERR_MSG
    SNAPSHOT_NAME (${SNAPSHOT_NAME}) can only be alpha-numeric '.' or '-'.
ERR_MSG
        exit 1
    fi
fi

if [[ -z "${VERSION_NUMBER}" ]]; then
    VERSION_NUMBER='0.0-0-1'
    INITIAL_CHANGLOG=1
fi

if [[ "$SHOW_VERSION" == "CURRENT" ]]; then
    # We are just going to show the verison and then exit.
    echo -n $VERSION_NUMBER
    exit 0
fi

if [[ -z "${PACKAGE_AUTHOR}" ]]; then
    PACKAGE_AUTHOR='gautam dey <gautam@deyfamily.org>'
fi

MAJOR_INC='$1'
MINOR_INC='$2+1'
PATCH_INC='0'
DEBIAN_INC='1'
# If there is a major change, signified by a commit message with
# "[changelog][major]", we will bump up the correct value.
git log ${STARTING_SHA1}..HEAD -i --grep '\[changelog\]\[major\]'
if [[ $? == 0 ]] && [[ -z "$UPDATE_TYPE" ]]; then
    UPDATE_TYPE="MAJOR"
fi

case $UPDATE_TYPE in
    "MAJOR")
        MAJOR_INC='$1+1'
        MINOR_INC='0'
    ;;
    "PATCH")
        PATCH_INC='$3+1'
        MINOR_INC='$2'
    ;;
    "PACKAGE")
        PATCH_INC='$3'
        DEBIAN_INC='$5+1'
    ;;
    "NONE")
        MINOR_INC='$2'
        PATCH_INC='$3'
        DEBIAN_INC='$5'
    ;;
esac

DATE=$(date +'%a, %d %B %Y %T %z')

NEXT_VERSION=$(perl -e "'$VERSION_NUMBER' =~ /^\s*(\d+)\.([\d.]+)-(\d+)(-(\d+))?(.*)?\s*\$/;printf(\"%u.%03u-%u-%u%s\",${MAJOR_INC},${MINOR_INC},${PATCH_INC},${DEBIAN_INC},'${SNAPSHOT_NAME}')")

if [[ "$SHOW_VERSION" == "NEXT" ]]; then
    # We are just going to show the verison and then exit.
    echo -n $NEXT_VERSION
    exit 0
fi

if [[ "$VERSION_NUMBER" == "$NEXT_VERSION" ]]; then
    # We are just going to output the old changelog.
    cat ${CHANGELOG_FILE}
    exit 0
fi

CURRENT_SHA1=$(git log -n 1 HEAD | grep commit | cut -d ' ' -f 2)

if [[ -z "$STARTING_SHA1" ]]; then
    STARTING_SHA1=$(
        git log -n 1 ${MASTER_BRANCH} -- ${CHANGELOG_FILE} \
        | grep commit                                      \
        | cut -d ' ' -f 2
    )
fi

LOG_BODY=$(
    git log ${STARTING_SHA1}..HEAD -i --grep '\[changelog\]' \
    | grep -iE '\[changelog\]|Merge pull request'            \
    | perl -pe 's/^\s*\[changelog\](.*)\s*$/  * $1\n/i'      \
    | perl -pe 's/^\s+(Merge pull request .*)\s*$/  $1/'
)

if [[ -z "${MESSAGE}" ]]; then
    LOG=$LOG_BODY
else
    LOG="  $MESSAGE
$LOG_BODY"
fi

cat <<ENTRY > ${TMPDIR:-/tmp}/$$.new
${PACKAGE_NAME} (${NEXT_VERSION}) ${PACKAGE_STABLE}; urgency=${PACKAGE_URGENCY}

  local package built: sha1 $CURRENT_SHA1
                      since $STARTING_SHA1

$LOG

 -- ${PACKAGE_AUTHOR}  ${DATE}

$CHANGELOG_OUT
ENTRY

#-------------------------------------------------------------------------------
cat ${TMPDIR:-/tmp}/$$.new $CHANGELOG_FILE
rm ${TMPDIR:-/tmp}/$$.new

exit 0