#387: make runOnlyOnce run on the first project (and make it work when maven's --projects param are specified)

[TheSnoozer]

Context

see: #387

In most cases this doesn't change much, however for some this might be considered a behavioral change (and thus fits a major version change). In specific when runOnlyOnce is specified the plugin will run on the first project as specified in the Reactor Build Order.

As per debugging project:

$ mvn clean package -Pgit-with-parent
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Build Order:
[INFO] 
[INFO] Git Commit Id Plugin Maven Mojo Debugging
[INFO] submodule-one
[INFO] submodule-two

or with --projects

$ mvn clean package -Pgit-with-parent --projects submodule-one,submodule-two
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Build Order:
[INFO] 
[INFO] submodule-one
[INFO] submodule-two

or vice versa (the pom.xml seems to take precedence):

$ mvn clean package -Pgit-with-parent --projects submodule-two,submodule-one
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Build Order:
[INFO] 
[INFO] submodule-one
[INFO] submodule-two

Inspired by sonar-scanner-maven plugin

Contributor Checklist

• Added relevant integration or unit tests to verify the changes
• Update the Readme or any other documentation (including relevant Javadoc)
• Ensured that tests pass locally: mvn clean package
• Ensured that the code meets the current checkstyle coding style definition: mvn clean verify -Pcheckstyle -Dmaven.test.skip=true -B

[TheSnoozer]

Perhaps think about this more: how should this interact with <skipPoms>true</skipPoms>?

[TheSnoozer]

Essentially the idea is that if skipPoms == true then the plugin attempts to find the first not pom project. If the skipPoms == false then the plugin retrieves the first project.

Note that whenever specifying the Maven's --projects param the order does not seem to make a difference (it seems that whatever is in the pom defined as order takes precedence).

e.g. this is the same:

mvn clean package -Pgit-with-parent --projects submodule-one,submodule-two
mvn clean package -Pgit-with-parent --projects submodule-two,submodule-one

Check also the Reactor Build Order at the start of the build:

[INFO] Reactor Build Order:
[INFO] 
[INFO] Git Commit Id Plugin Maven Mojo Debugging
[INFO] submodule-one
[INFO] submodule-two