Document Maven execution ids in more detail

[unix-junkie]

What's done:

• Added the use cases (with examples) where executionId is indeed necessary.

[petertrr]

Does it always use default default settings, even if custom configuration is tied to the same execution phase?

[unix-junkie]

Whenever an execution is bound to a Maven phase, the executionId becomes irrelevant (and unnecessary).

Alternatively, if you don't bind a specific execution to a phase, the default executionId will be default-cli:

$ mvn diktat:check
[INFO] Scanning for projects...
[INFO]
[INFO] ---------------< org.cqfn.diktat:diktat-examples-maven >----------------
[INFO] Building diktat-examples-maven 1.1.0-SNAPSHOT
[INFO] --------------------------------[ pom ]---------------------------------
[INFO]
[INFO] --- diktat-maven-plugin:1.1.0:check (default-cli) @ diktat-examples-maven ---
[INFO] Running diKTat plugin with configuration file /home/alice/diktat-example-maven/foo.yml and inputs [/home/alice/diktat-example-maven/diktat-example
-maven/src/main/kotlin]
[WARNING] Not going to check indentation because there are tabs
[WARNING] You have enabled TRAILING_COMMA, but rule will remain inactive until you explicitly set configuration options. See [available-rules.md] for possible configuration options.
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  2.467 s
[INFO] Finished at: 2022-05-26T19:05:49+03:00
[INFO] ------------------------------------------------------------------------

So, technically, you can create a custom configuration with such a default name, but I doubt Maven has any kind of contract for this behaviour. I mean, we probably shouldn't rely on this, as it may change (and break).

[nulls]

Looks like default-cli is part of official maven documentation: https://maven.apache.org/guides/mini/guide-default-execution-ids.html

[codecov]

Codecov Report

Merging #1308 (ec11c35) into master (23ebf80) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #1308   +/-   ##
=========================================
  Coverage     82.01%   82.01%           
  Complexity     2530     2530           
=========================================
  Files           105      105           
  Lines          7201     7201           
  Branches       2058     2058           
=========================================
  Hits           5906     5906           
  Misses          346      346           
  Partials        949      949           

Flag	Coverage Δ
unittests	82.01% <ø> (ø)

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