One of the Parrot Configure.pl tasks runs:

rakudo/parrot/config/auto/git_describe.pm

auto::git_describe uses Parrot::Git::Describe::current; which runs `git describe --tags` and puts the result of that command in a file .parrot_current_git_describe

Similar thing happens for .parrot_current_sha1

However, auto::git_describe will skip this unless a .git directory exists in the parrot directory. For Rakudo Star this .git directory doesn't exist as part of a Parrot release, so the git_describe step is skipped. This means that .parrot_current_git_describe doesn't get generated as part of parrot Configure.pl, which in turn means that the current git revision isn't built into the parrot config hash.

e.g. for a Rakudo Star build,

$ ./parrot_config git_describe
 no such key: 'git_describe'

Rakudo tries to use this information when it reports the version number via `perl6 --version`.

Either this information needs to be made available to auto::git_describe for Rakudo Star distributions using a bundled Parrot release (which is not a git repo), or the code to handle to --version in src/Perl6/Compiler.pir needs to be improved (see an example patch below, 0001-Perl6-Compiler-Parrot-revision-for-version-fix.patch)