Added CHANGELOG function

A basic function to generate CHANGELOG.md from the last 25 commits in a
repository.

.shell_functions

@@ -97,3 +97,18 @@ testmerge() {
     git diff --cached
     echo "'git merge --abort' when done"
 }
+
+git_changelog() {
+  echo "# Last 25 Commits" > CHANGELOG.md # Add the header
+  git log --pretty=format:"%h|%ad|%an|%s" --date=short -n 25 | \
+    awk -F'|' '{
+      printf "## %s (%s, %s) - %s\n\n", $1, $3, $2, $4;
+      commit_hash = $1;
+      cmd = "git show -s --format='%x09%b' " commit_hash;
+      while ((cmd | getline line) > 0) {
+        printf "%s\n", line;
+      }
+      close(cmd);
+      printf "\n";
+    }' >> CHANGELOG.md
+}