git: openjdk/skara: Add support for Mercurial

[duke]

Changeset: d14976eb
Author:    Erik Helin <ehelin at openjdk.org>
Date:      2019-09-10 07:39:29 +0000
URL:       https://github.com/openjdk/skara/commit/d14976eb

Add support for Mercurial

Reviewed-by: rwestberg

! cli/src/main/java/org/openjdk/skara/cli/GitFork.java
! cli/src/main/java/org/openjdk/skara/cli/GitPr.java
! cli/src/main/java/org/openjdk/skara/cli/GitWebrev.java
+ skara.py