RFR: 8253034: Update symbol generation to accomodate Git as the SCM

[Erik Helin]

On Tue, 15 Sep 2020 01:19:32 GMT, Aditya Mandaleeka <adityam at openjdk.org> wrote:

>> The symbol generation script assumed Mercurial was being used as the SCM. This should now be updated to Git.
>
> make/scripts/generate-symbol-data.sh line 66:
> 
>> 64: fi;
>> 65:
>> 66: if [ "`git status -s .`x" != "x" ] ; then
> 
> Just a suggestion: perhaps you want to use the porcelain format here instead of short?
> https://git-scm.com/docs/git-status#Documentation/git-status.txt---porcelainltversiongt

I agree with @adityamandaleeka, please use `git status --porcelain=v1`. See the git status
[documentation](https://git-scm.com/docs/git-status#_porcelain_format_version_1) for the specification for the output.

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PR: https://git.openjdk.java.net/jdk/pull/161