[FEATURE] initial implementation of generating a changelog via a script (- #155 -)

Additions with file generate_changelog.sh:
 * initial implementation

Author: reactive-firewall

generate_changelog.sh

@@ -0,0 +1,65 @@
+#! /bin/bash
+
+function id_current_tag() {
+	local INPUT="${1}"
+	git describe --tags --abbrev=0 ${INPUT}
+}
+
+function enumerate_tag_history() {
+	local HEAD_TAG=$(id_current_tag HEAD)
+	{ git rev-list --tags --ancestry-path "$(git tag --no-contains "${HEAD_TAG}" | sort -V | head -n1)^..HEAD" ; wait ;} | xargs -I{} git tag --points-at "{}" 2>/dev/null ;
+	wait ;
+}
+
+# step 1: is designed to determine the current and previous Git tags and
+# then construct a Git range based on these tags. If no argument is provided, it defaults to
+# using the tags.
+if [[ -z "${1}" ]] ; then
+GIT_CURRENT_TAG=$(id_current_tag)
+GIT_PREVIOUS_TAG=$(enumerate_tag_history | grep -A 1 -F -f <(git describe --tags --abbrev=0 "${GIT_CURRENT_TAG}") | tail -n1 )
+FALLBACK_GIT_RANGE="${GIT_CURRENT_TAG}...${GIT_PREVIOUS_TAG}"
+fi ;
+GIT_RANGE="${1:-${FALLBACK_GIT_RANGE}}"
+
+# cache the git log
+CHANGELOG_BUFFER=".chagelog_buffer.txt"
+cat <(git log "${GIT_RANGE}" --reverse --pretty=format:"COMMIT_START%n%h%n%B%nCOMMIT_END") >"${CHANGELOG_BUFFER}" ; wait ;
+
+printf "%s\n\n" "## What Changed between \`${GIT_RANGE}\`" ;
+
+# auto-collect gitlog
+for FILE_INPUT in $(git log --pretty=format:"%n" --name-only "${GIT_RANGE}" | sort -id | uniq) ; do
+
+if [[ ( -n "$FILE_INPUT" ) ]] ; then
+
+awk -v RS='' -v ORS='\n\n\n' -v filename="$FILE_INPUT" '
+    {
+        # Check if the block contains a valid change-log entry
+        if ($0 ~ /((Changes in)|(Additions with)|(Deletions from)) file/ && $0 ~ filename) {
+            # Ensure that there is no content before the match
+            if ($0 ~ /^[[:space:]]*((Changes in)|(Additions with)|(Deletions from))/) {
+                # Extract the header (first line) and the content
+                header = $0; 
+                header_line = substr(header, 1, index(header, ":") - 1);  # Get the header
+                if (header_line ~ filename) {
+                    content = substr(header, index(header, ":") + 1);  # Get the content after the header
+                    # Combine the header and content
+                    combined[header_line] = (combined[header_line] ? combined[header_line] "\n" : "") content;
+                }
+            }
+        }
+    }
+    END {
+        # Print combined entries
+        for (h in combined) {
+            print h ":" combined[h]
+        }
+    }
+' <"${CHANGELOG_BUFFER}" | sort -id | uniq | sort -rd
+
+fi ;
+
+done ;
+
+# remove the buffer
+rm -f "${CHANGELOG_BUFFER}" 2>/dev/null || : ;