Quick and dirty tag and release notes git plugin. Put in path and chmod +x it. git tagrelease -h for instructions.

git-tagrelease

#!/bin/bash

VERSION="20170125"
OUTPUT_FILE="./RELEASE_NOTES.md"

usage() {
    cat << __EOF
git tagrelease usage:

    git tagrelease [options]

Where [options] include:

    -f|--from TAG     When generating release notes, start from
                      this tag
    -t|--to TAG       When generating release notes, end at
                      this tag
    -n|--name NAME    Tag name
    -o|--output FILE  Output to this file, default $OUTPUT_FILE
    -d|--dry-run      Do a dry run
    -i|--ignoredirty  Ignore dirty index (uncommitted changes)
    -h|--help         Show this help

If a -t tag is not specified, release note generation will be from the
tag specified using -f. If both or only -t are specified, TAG_NAME will be
ignored and not used to commit the new release notes and tag the
commit. If -i is specified, anything staged for commit will be committed
with the new release notes.

__EOF

    exit 1
}

FROM_TAG=""
TO_TAG=""
TAG_NAME=""
DRY_RUN=""
IGNORE_DIRTY=""

while [ $# -ge 1 ]; do
    key="$1"
    shift

    case $key in
        -f|--from)
            FROM_TAG="$1"
            shift
            ;;
        -t|--to)
            TO_TAG="$1"
            shift
            ;;
        -n|--name)
            TAG_NAME="$1"
            shift
            ;;
        -o|--output)
            OUTPUT_FILE="$1"
            shift
            ;;
        -d|--dry-run)
            DRY_RUN="1"
            ;;
        -i|--ignoredirty)
            IGNORE_DIRTY="1"
            ;;
        -h|--help)
            usage
            ;;
        *)
            if [ -z $TAG_NAME ]; then
                TAG_NAME=$key
            else
                usage
            fi
            ;;
    esac
done

if [ -n "$FROM_TAG" ] && [ -n "$TO_TAG" ]; then
    TAG_NAME=""
fi

if [ -z "$TAG_NAME" ] && [ -z "$FROM_TAG" ] && [ -z "$TO_TAG" ]; then
    usage
fi

if [ -z $IGNORE_DIRTY ]; then
    if output=$(git status --untracked-files=no --porcelain) && [ -z "$output" ]; then
        echo "Working directory is clean."
    else
        echo "You have uncommitted changes."

        exit 1
    fi
fi

if ! [ -z $DRY_RUN ]; then
    if ! [ -z "$FROM_TAG" ] && [ -n "$TO_TAG" ]; then
        echo "## $TO_TAG"
        git log "$FROM_TAG".."$TO_TAG" --no-merges --format="  - %s"
    elif [ -n "$TO_TAG" ]; then
        echo "## $TO_TAG"
        git log "$TO_TAG" --no-merges --format="  - %s"
    elif [ -z "$TAG_NAME" ]; then
        echo "Missing tag name, aborting."
        exit 1
    else
        echo "## $TAG_NAME"
        git log "$FROM_TAG".. --no-merges --format="  - %s"
    fi

    echo ""
else
    tmpfile=$(mktemp "/tmp/$(basename $0).XXXXXX")

    echo "Generating $OUTPUT_FILE"

    if [ -n "$FROM_TAG" ] && [ -n "$TO_TAG" ]; then
        echo "## $TO_TAG" >>"$tmpfile"
        git log "$FROM_TAG".."$TO_TAG" --no-merges --format="  - %s" >>"$tmpfile"
    elif [ -n "$TO_TAG" ]; then
        echo "## $TO_TAG" >>"$tmpfile"
        git log "$TO_TAG" --no-merges --format="  - %s" >>"$tmpfile"
    elif [ -z "$TAG_NAME" ]; then
        echo "Missing tag name, aborting."
        exit 1
    else
        echo "## $TAG_NAME" >>"$tmpfile"
        git log "$FROM_TAG".. --no-merges --format="  - %s" >>"$tmpfile"
    fi

    echo "" >>"$tmpfile"

    if [ -f "$OUTPUT_FILE" ]; then
        mv -f "$OUTPUT_FILE" "$OUTPUT_FILE.old"
        cat "$tmpfile" "$OUTPUT_FILE.old" >> "$OUTPUT_FILE"
        rm -f "$OUTPUT_FILE.old"
    else
        cp "$tmpfile" "$OUTPUT_FILE"
    fi

    rm -f "$tmpfile"

    if ! [ -z "$TAG_NAME" ]; then
        echo "Committing $OUTPUT_FILE and tagging release."
        git add "$OUTPUT_FILE"
        git commit -am "Release $TAG_NAME"
        git tag "$TAG_NAME" -m "Release $TAG_NAME"
    fi
fi

echo "Done."
echo ""