How can I limit a Jenkins build step to ONLY given changeset?

Question

I'm using Jenkins declarative pipeline and I'm trying to execute a specific build stage only if changes were made ONLY in a specified directory.

So my directory hierarchy looks something like this:

root
 ├─ some-directory
 |   ├─ sub-directory
 |   |   └─ file-1
 |   ├─ file-1
 |   └─ file-2
 ├─ another-directory
 |   ├─ file-1
 |   └─ file-2
 ├─ file-x
 └─ file-y

This is the current code:

stage ("Deploy branches") {
    agent any

    when { 
        allOf {
            not { branch 'master' }
            changeset "some-directory/**"
        }
    }

    steps {
        // do stuff
    }
}

This deploys whenever something was changed in "some-directory" but also when something outside of "some-directory" was changed. I would like this step to run if nothing else but the contents of "some-directory" were changed.

This is what the Jenkins docs say about the "changeset" directive:

changeset

Execute the stage if the build’s SCM changeset contains one or more files matching the given string or glob. Example: when { changeset "**/*.js" }

By default the path matching will be case insensitive, this can be turned off with the caseSensitive parameter, for example: when { changeset glob: "ReadMe.*", caseSensitive: true }

"If the changeset contains one or more files matching the given string or glob." means the pipelines works as designed, but what I nwould eed is

"If the files in the changeset match only the given string or glob."

Unfortunately I couldn't find anything about that in the docs or somewhere else on the internet.

Do you have any suggestions how I could make this possible?

Answer 1

I believe that changeset cannot do what you are trying to achieve ; but it can be replaced with an expression shelling out to compute the Git diff and do the relevant filtering. I had a similar issue and it worked fine for me.

The following should work for your use-case:

stage ("Deploy branches") {
    agent any

    when { 
        allOf {
            not { branch 'master' }
            changeset "some-directory/**"
            expression {  // there are changes in some-directory/...
                sh(returnStatus: true, script: 'git diff  origin/master --name-only | grep --quiet "^some-directory/.*"') == 0
            }
            expression {   // ...and nowhere else.
                sh(returnStatus: true, script: 'git diff origin/master --name-only | grep --quiet --invert-match "^some-directory/.*"') == 1
            }
        }
    }

    steps {
        // do stuff
    }
}

(this hardcodes the comparison with origin/master, which was my use-case ; if that’s not sophisticated enough it might be possible to use some Jenkins variable containing the target branch of the pull-request.)