RFR: SKARA-461: Do a git version check

[Jorn Vernee]

On Wed, 29 Jul 2020 15:19:38 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> How hard would it be to actually support older versions? Requiring 2.22 might be a barrier for some users. I just
>> checked and 2 of the 4 machines I use, including my main development platform, have versions older than that. I'm not a
>> heavy user of the Skara CLI tools, but am concerned about those who are.
>
> Btw, I think this PR is fine unless / until the Skara CLI tools support older versions.

@kevinrushforth Thanks for taking a look.

My intent was not to say the CLI tools should require 2.22 or some other version, but the current list of known working
versions is adjusted to the fact that the current implementation requires version 2.22 to run successfully (otherwise
e.g. https://bugs.openjdk.java.net/browse/SKARA-454 can occur).

I think the intent was to support older versions as well, since a lot of package managers provide older versions of
git, but currently using a version older than 2.22 causes problems. I've added the other versions to the code as well,
but commented them out for now.

The required version should probably be adjusted downwards once lesser versions have been confirmed to work. (i.e. this
is more of a stopgap solution)

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PR: https://git.openjdk.java.net/skara/pull/707