Remove redundant gradle_version property

[Goooler]

It's easy to forget to modify this property, and we have no much necessary to input it for Wrapper tasks.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (d547089) 68.5316% compared to head (18a66e3) 68.5219%.

Additional details and impacted files

@@                Coverage Diff                 @@
##               master      #2050        +/-   ##
==================================================
- Coverage     68.5316%   68.5219%   -0.0097%     
+ Complexity      29174      29170         -4     
==================================================
  Files            1422       1422                
  Lines          113482     113482                
  Branches        19548      19548                
==================================================
- Hits            77771      77760        -11     
- Misses          29174      29181         +7     
- Partials         6537       6541         +4     

see 4 files with indirect coverage changes

[paulk-asert]

I don't think we can remove this. Current ASF policy prohibits binary files like the wrapper jar from being included in the src zip. So, to build from source, we need to have the bootstrap step. Here is where we exclude 'wrapper' (which contains version in properties file):
https://github.com/apache/groovy/blob/master/subprojects/groovy-binary/build.gradle#L184
Best bet is to only update version using bootstrap step - though I realise that isn't what dependabot et al will use or the standard instructions from Gradle.
There are other approaches to solve the problem, which I guess we could relook at, but it wouldn't be (just) the change suggested here.

[Goooler]

If we can remove that line to prevent gradle/wrapper been deleted?

[paulk-asert]

That is the spec for building the source zip. As per ASF requirements, it can't contain binary files, e.g. gradle-wrapper.jar. We have asked for an exemption in the past but haven't been successful. ASF values highly the "openness" of the source zip. The implication is that anyone should be able to look at the files used within the source zip when building from source and understand what everything does without having to try to work out what might be inside any binary object such as a jar.

[Goooler]

Got it! Thanks for your explanation.

[aalmiray]

FWIW I followed the trail of the Maven wrapper to bootstrap it from source. The initial commit is here jreleaser/jreleaser@82f0706 with updates posted a few times later. In case you'd like to do something similar.