How to trigger a build only if changes happen on particular set of files

If you are using a declarative syntax of Jenkinsfile to describe your building pipeline, you can use changeset condition to limit stage execution only to the case when specific files are changed. This is now a standard feature of Jenkins and does not require any additional configruation/software.

stages {
    stage('Nginx') {
        when { changeset "nginx/*"}
        steps {
            sh "make build-nginx"
            sh "make start-nginx"
        }
    }
}

You can combine multiple conditions using anyOf or allOf keywords for OR or AND behaviour accordingly:

when {
    anyOf {
        changeset "nginx/**"
        changeset "fluent-bit/**"
    }
}
steps {
    sh "make build-nginx"
    sh "make start-nginx"
}

The Git plugin has an option (excluded region) to use regexes to determine whether to skip building based on whether files in the commit match the excluded region regex.

Unfortunately, the stock Git plugin does not have a "included region" feature at this time (1.15). However, someone posted patches on GitHub that work on Jenkins and Hudson that implement the feature you want.

It is a little work to build, but it works as advertised and has been extremely useful since one of my Git trees has multiple independent projects.

https://github.com/jenkinsci/git-plugin/pull/49

Update: The Git plugin (1.16) now has the 'included' region feature.