github.com/cockroachdb/cockroach@v20.2.0-alpha.1+incompatible/githooks/commit-msg

#!/usr/bin/env bash
#
# -u: we want the variables to be properly assigned.
# -o pipefail: we want to test the result of pipes.
# No -e because we have failing commands and that's OK.
set -uo pipefail

grep=${GREP:-grep}
awk=${AWK:-awk}
sed=${SED:-sed}

# Support both terminfo and termcap.
# We want to check whether stderr is a terminal (to enable
# printing colors). We want this test to work even if stdin is
# redirected (e.g. when run from git commit) or stdout is
# redirected (e.g. in the var assignments below).
red=$([ -t 2 ] && { tput setaf 1 || tput AF 1; } 2>/dev/null)
reset=$([ -t 2 ] && { tput sgr0 || tput me; } 2>/dev/null)
warn() {
    echo >&2
    echo "${red}$*${reset}" >&2
    echo >&2
}

if ! test -s "$1"; then
	warn "commit message is empty!"
	# nothing to check further.
	exit 0
fi

# First lint test: give a friendly reminder on long lines.

longlines=$($awk '/^# --* >8 --*/ {exit} /^[^#]/ { if (length() >= 80) print }' <"$1")
if test -n "$longlines"; then
    warn "Long line(s) detected:"
    echo "$longlines" | $sed -e 's/^/   /g' >&2
    echo >&2
    echo "Please amend and wrap long lines." >&2
    echo "(Long lines are OK if inside a preformatted block or a table.)" >&2
    echo >&2
fi

# Lint the release notes.
#
# It's OK to have multiple entries per commit
# (e.g. changes in different categories). But that means we need to
# extract them separately for analysis.
#
saveIFS=$IFS
IFS='
'
notes=($($grep -iE '^release note' "$1"))

# Set this to 1 to require a release justification note.
require_justification=0
justification=($($grep -iE '^release justification: \S+' "$1"))

IFS=$saveIFS

informed=
inform() {
    if [ -z "$informed" ]; then
        info=${rnote:0:40}
        if [ "$info" != "$rnote" ]; then info="$info..."; fi
        warn "Warning: malformed release note entry: $info"
    fi
    informed=1
}
hint() {
    inform
    echo "- $*" >&2
}

if [ "$require_justification" = 1 -a  0 = ${#justification[*]} ]; then
    warn "No release justification specified."
    echo "Try: 'Release justification: This commit is safe for this release because..." >&2
    echo >&2
fi

if [ 0 = ${#notes[*]} ]; then
    warn "No release note specified."
    echo "Try: 'Release note (...): ...'" >&2
    echo >&2
else
    for rnote in "${notes[@]}"; do
        informed=
        if echo "$rnote" | $grep -qiE '^release note' && ! echo "$rnote" | $grep -qE '^Release note'; then
            hint "case matters! Try '${rnote:0:12}' -> 'Release note'"
        fi
        if echo "$rnote" | $grep -qiE '^release notes'; then
            hint "singular please. Use multiple entries if there are multiple notes. Try '${rnote:0:13}' -> 'Release note'"
        fi
        if echo "$rnote" | $grep -qiE '^release notes? *: *\('; then
            entered=$(echo "$rnote" | cut -d')' -f1)\); entered=${entered:0:40}
            cat=$(echo "$rnote" | cut -d'(' -f2 | cut -d')' -f1)
            hint "place the category before the colon. Try '$entered' -> 'Release note ($cat):'"
        fi
        if echo "$rnote" | $grep -qiE '^release notes? *: *[^ ]* *:'; then
            cat=$(echo "$rnote" | $sed -e 's/^[^:]*: *//g;s/ *:.*$//g')
            entered=$(echo "$rnote" | cut -d: -f1-2)
            hint "place category within parentheses. Try '$entered:' -> 'Release note ($cat):'"
        fi
        if echo "$rnote" | $grep -qiE '^release notes?[^:]*: *none' && ! echo "$rnote" | $grep -qE '^Release note: [nN]one'; then
            entered=$(echo "$rnote" | $sed -e 's/none.*/none/ig')
            hint "for no release notes use 'none' with no category. Try '$entered' -> 'Release note: none'"
        fi
        if ! echo "$rnote" | $grep -qiE '^release notes? *: *none' && echo "$rnote" | $grep -qiE '^release notes? *: *[^( ]'; then
            entered=$(echo "$rnote" | cut -d: -f2-); entered=${entered:0:40}
            hint "category missing (can only be omitted if note is 'none'). Try 'Release note (category):$entered'"
        fi
        if echo "$rnote" | $grep -qiE '^release notes?[^:]*:([^ ]|   *)' || \
                echo "$rnote" | $grep -qiE '^release notes?(\(|  +\()' || \
                echo "$rnote" | $grep -qiE '^release notes? *\( +' || \
                echo "$rnote" | $grep -qiE '^release notes? *\( *[^)]* +\)' ; then
            entered=${rnote:0:40}
            body=$(echo "$rnote"| cut -d: -f2-|cut -c1-40|$sed -e 's/^ *//g')
            cat=$(echo "$rnote" | cut -d'(' -f2 |cut -d')' -f1|$sed -e 's/^ *//g;s/ *$//g')
            if test -z "$cat"; then cat=...; fi
            hint "some space problem. Try '$entered' -> 'Release note ($cat): $body'"
        fi
        # Now prune the category
        if echo "$rnote" | $grep -qiE '^release notes? *\([^)]*\)'; then
            cat=$(echo "$rnote" | cut -d'(' -f2|cut -d')' -f1|$sed -e 's/^ *//g;s/ *$//g')
            lower=$(echo "$cat"|tr A-Z a-z)
            if [ "$cat" != "$lower" ]; then
                hint "categories in lowercase. Try 'Release note ($cat)' -> 'Release note ($lower)'"
            fi
            if echo "$rnote" | $grep -qiE '^release notes? *\([^)/]*/'; then
                repl=$(echo "$lower"|$sed -e 's| */ *|, |g')
                hint "use commas to separate categories. Try '($lower)' -> '($repl)'"
                lower=$repl
            fi
            saveIFS=$IFS
            IFS='
'
            cats=($(echo "$lower" | tr ',' '\n' | $sed -e 's/^ *//g'))
            IFS=$saveIFS
            for lcat in "${cats[@]}"; do
                case $lcat in
                    "cli change") ;;
                    "sql change") ;;
                    "admin ui change") ;;
                    "general change") ;;
                    "build change") ;;
                    "enterprise change") ;;
                    "backward-incompatible change") ;;
                    "performance improvement") ;;
                    "bug fix") ;;
                    "security update") ;;
                    bugfix)
                        hint "Try 'Release note (bugfix)' -> 'Release note (bug fix)'" ;;
                    security*)
                        hint "Try 'Release note ($lcat)' -> 'Release note (security update)'" ;;
                    sql*)
                        hint "Try 'Release note ($lcat)' -> 'Release note (sql change)'" ;;
                    "backwards-incompatible"*|"backward incompatible"*)
                        hint "Try '$lcat' -> 'backward-incompatible change'" ;;
                    *) hint "unknown category '$lcat'" ;;
                esac
            done
        fi
	# Do some linting on the message itself.
	msg=$(echo "$rnote" | cut -d':' -f1-)
	if echo "$msg" | $grep -qiE ' *([cC]loses?|[fF]ix(es)?) *#[0-9]+\.? *'; then
	    hint "don't just close or fix. Explain."
	fi
    done
    if test -n "$informed"; then echo >&2; fi
fi