RFR: git-webrev: add --json flag

[Robin Westberg]

On Sat, 15 Aug 2020 10:49:14 GMT, Erik Helin <ehelin at openjdk.org> wrote:

> Hi all,
> 
> please review this patch that adds the `--json` flag to `git-webrev`. The `--json` flag is not meant to be used by a
> humans, it generates a JSON version of a "webrev" that tools can consume (in comparison to HTML that is usually
> generated).  Testing:
> - [x] Manual testing on Linux x64
> 
> Thanks,
> Erik

Looks good!

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Marked as reviewed by rwestberg (Reviewer).

PR: https://git.openjdk.java.net/skara/pull/717