Refine post-merge hook script

[philhagen]

Add conditional handling so e.g. logstash only restarts if its configuration files changed, etc.

See https://stackoverflow.com/questions/4877306/list-changed-files-in-git-post-merge-hook

[philhagen]

possibly better approach:

#!/bin/bash

# Get the list of changed files
changed_files=$(git diff --cached --name-only)

# Check if specific files are changed
if echo "$changed_files" | grep -q "path/to/specific/file.txt"; then
    # Run your desired command
    echo "Specific file changed, running checks..."
    # For example, run linters or tests
    # ...
fi