[Rev 01] RFR: git-sync should use APIs to find upstream

[Erik Helin]

The pull request has been updated with additional changes.

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Added commits:
 - a5632222: Use .orElseThrow() instead of .get()

Changes:
  - all: https://git.openjdk.java.net/skara/pull/262/files
  - new: https://git.openjdk.java.net/skara/pull/262/files/20e4e200..a5632222

Webrevs:
 - full: https://webrevs.openjdk.java.net/skara/262/webrev.01
 - incr: https://webrevs.openjdk.java.net/skara/262/webrev.00-01

  Stats: 8 lines in 3 files changed: 2 ins; 0 del; 6 mod
  Patch: https://git.openjdk.java.net/skara/pull/262.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/262/head:pull/262

PR: https://git.openjdk.java.net/skara/pull/262