Breaks with SHA longer than 8

[alexander-bunkenburg-chartboost]

The "git describe --abbrev=8" returns a SHA with length 8 or more if necessary.

I hit a case where 9 was necessary: "v1.0.20220610+60-97fed8831".

Parsing the SHA in GitDescribeOutput.parse assumes it's exactly 8 characters long.

[bursauxa]

Encountered today, the issue still happens.

[dgolda]

I just encountered this bug in version 5.1.0 and lost 2 hours because of it. I think it’s worth releasing a version where this is already fixed.

[eed3si9n]

Released https://github.com/sbt/sbt-dynver/releases/tag/v5.1.1