Log git info

Debug log the buildpack's git remotes and HEAD commit. There is no
point looking for other commits as Cloud Foundry creates only a
shallow clone of the buildpack.

[#53863269]
Merge 53863269-stale-fork-diagnostics to master

[Completes #53863269]
Revert "Log git info"

This reverts commit cfc217472e058c295b697bbc87e5a67b748c4d1b.
Log git info

Debug log the buildpack's git remotes and HEAD commit. There is no
point looking for other commits as Cloud Foundry creates only a
shallow clone of the buildpack.

[#53863269]
Merge 53863269- to master

[Completes #53863269]
Enforce public API documentation

Add Rake task to police API documentation. Fail the Rake build with
statistics and list of undocumented objects if the API is not 100%
documented, but output statistics in the successful case.

Suppress the statistics in the yardoc task to avoid duplicate output.

Add missing public API documentation

[#55005634]
Merge 55005634-public-API-check to master

[Completes #55005634]
Repository builder documentation update

This change updates the repository builder documentation to point at
the new combined repository.

[#55068502]
Merge 55068502-update-documentation to master

[Completes #55068502]
fix typo
Specify port for Spring Boot Java Main applications

Detect such applications by specific Spring Boot main classnames.

[#55145080]
Merge 55145080-spring-boot-java-main to master

[Completes #55145080]
Hide constructors of utility classes

Hide the constructors of utility classes which should not be
instantiated.
Format backtraces properly

Also add some missing unit tests of Buildpack.

[#53870297]
Merge 53870297- to master

[Completes #53870297]
Fix OpenJDK JRE versions

Previously, Groovy applications that use @Grab were affected by
problems in the _25 version of the JRE.  This change fixes the version
of the JRE to _21 until those bugs are fixed.

[#55382524]
Merge 55382524-fix-openjdk-version to master

[Completes #55382524]
Use Spring CLI TAR file

This change causes the Spring Boot CLI container to use a TAR file
rather than a ZIP file.  This simplifies the extraction process.

[#55377304]
Merge 55377304-spring-boot-tar to master

[Completes #55377304]
Handle buildpack not in a git repository

When the buildpack is not in a git repository, issue an appropriate
debug log message and prevent 'fatal' standard error messages from
appearing.

Improve test coverage of Buildpack class.

[#55742000]