feat: initial rpm-changelog composite action

Generates an rpm %changelog entry from git history and prepends it
to the target spec file. Runs in release CI so every tag push gets
a fresh dated entry covering the commits since the previous matching
tag. Avoids stale dates, forgotten bumps, and bogus-weekday warnings.

Inputs: spec path, version, optional release suffix, author,
tag-pattern, exclude-patterns. The last two make the defaults (v*
tags, filter bump-version chores and merges) tweakable for projects
with different conventions.

Migrated from inline logic in helexa/cortex so any project can
adopt the same pattern with a single uses: reference.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/generate-rpm-changelog.sh

@@ -0,0 +1,86 @@
+#!/bin/bash
+# Generate an rpm %changelog entry for this release and prepend it to
+# the spec's existing %changelog section.
+#
+# Usage: generate-rpm-changelog.sh <spec-file> <version>
+#
+# Environment overrides:
+#   CHANGELOG_AUTHOR  — "Name <email>", default "Gitea Actions <actions@git.lair.cafe>"
+#   RELEASE           — release suffix, default "1"
+#   TAG_PATTERN       — glob for release tags, default "v*"
+#   EXCLUDE_PATTERNS  — newline-separated grep -E patterns to drop
+#
+# Collects commits since the previous matching tag, drops filtered
+# lines (bump-version chore commits, merges, etc.), and writes a
+# dated entry.
+
+set -euo pipefail
+
+SPEC="$1"
+VERSION="$2"
+AUTHOR="${CHANGELOG_AUTHOR:-Gitea Actions <actions@git.lair.cafe>}"
+RELEASE="${RELEASE:-1}"
+TAG_PATTERN="${TAG_PATTERN:-v*}"
+EXCLUDE_PATTERNS="${EXCLUDE_PATTERNS:-$'^- chore: bump version\n^- Merge'}"
+
+if [ ! -f "$SPEC" ]; then
+  echo "error: spec file not found: $SPEC" >&2
+  exit 1
+fi
+
+if ! grep -q '^%changelog' "$SPEC"; then
+  echo "error: no %changelog section in $SPEC — refusing to mangle" >&2
+  exit 1
+fi
+
+# Find the previous release tag (exclude the current tag at HEAD).
+PREV_TAG=$(git describe --tags --abbrev=0 --match="$TAG_PATTERN" HEAD^ 2>/dev/null || echo "")
+
+if [ -n "$PREV_TAG" ]; then
+  RAW=$(git log --no-merges --pretty=format:'- %s' "${PREV_TAG}..HEAD")
+
+  # Build a combined grep -E pattern from the exclude list; drop blanks.
+  COMBINED=""
+  while IFS= read -r pat; do
+    [ -z "$pat" ] && continue
+    if [ -z "$COMBINED" ]; then
+      COMBINED="$pat"
+    else
+      COMBINED="${COMBINED}|${pat}"
+    fi
+  done <<< "$EXCLUDE_PATTERNS"
+
+  if [ -n "$COMBINED" ]; then
+    LOG=$(printf '%s\n' "$RAW" | grep -Ev "$COMBINED" || true)
+  else
+    LOG="$RAW"
+  fi
+else
+  LOG=""
+fi
+
+if [ -z "$LOG" ]; then
+  LOG="- No user-visible changes"
+fi
+
+DATE=$(LC_ALL=C date -u +'%a %b %d %Y')
+ENTRY="* ${DATE} ${AUTHOR} - ${VERSION}-${RELEASE}
+${LOG}
+"
+
+# Prepend the entry to the %changelog section.
+TMP=$(mktemp)
+awk -v entry="$ENTRY" '
+  inserted == 0 && /^%changelog[[:space:]]*$/ {
+    print
+    print entry
+    inserted = 1
+    next
+  }
+  { print }
+' "$SPEC" > "$TMP"
+
+mv "$TMP" "$SPEC"
+
+echo "Added changelog entry for ${VERSION}-${RELEASE}:"
+echo "$ENTRY"