Support git 2.15 and newer

The 2.15 release of git drops support for `git branch --set-upstream`
and replaces it with `git branch --set-upstream-to` which was added in
git 1.8. Move from --set-upstream to --set-upstream-to in order to
support git 2.15 and beyond. Note that this specifically affects the
`git review -d` functionality as it is what needs to update the
upstream.

This does drop support for git 1.7 and older though as this option did
not exist then. Polling linux distros and OS X the oldest git I can find
is on CentOS 7 which has 1.8 so this should be fine.

Story: 2001266
Co-Authored-By: Harry Mallon <Harry.Mallon@codex.online>
Change-Id: I5ded1ab39bb2c76bdc38655299bac11b4584e138

doc/source/installation.rst

@@ -16,6 +16,8 @@ For assistance installing pacakges from ``pypi`` on your OS check out
 For installation from source simply add ``git-review`` to your $PATH
 after installing the dependencies listed in requirements.txt
 
+.. note:: ``git-review`` requires git version 1.8 or greater.
+
 Setup
 =====
 

git_review/cmd.py

@@ -1227,11 +1227,11 @@ def checkout_review(branch_name, remote, remote_branch):
         run_command_exc(CheckoutNewBranchFailed,
                         "git", "checkout", "-b",
                         branch_name, "FETCH_HEAD")
-        # --set-upstream-to is not supported in git 1.7
+        # --set-upstream-to is supported starting in git 1.8
         run_command_exc(SetUpstreamBranchFailed,
-                        "git", "branch", "--set-upstream",
-                        branch_name,
-                        '%s/%s' % (remote, remote_branch))
+                        "git", "branch", "--set-upstream-to",
+                        '%s/%s' % (remote, remote_branch),
+                        branch_name)
 
     except CheckoutNewBranchFailed as e:
         if re.search("already exists\.?", e.output):

git_review/tests/test_git_review.py

@@ -310,9 +310,9 @@ class GitReviewTestCase(tests.BaseGitReviewTestCase):
         # track different branch than expected in changeset
         branch = self._run_git('rev-parse', '--abbrev-ref', 'HEAD')
         self._run_git('branch',
-                      '--set-upstream',
-                      branch,
-                      'remotes/origin/other')
+                      '--set-upstream-to',
+                      'remotes/origin/other',
+                      branch)
         self.assertRaises(
             Exception,  # cmd.BranchTrackingMismatch inside
             self._run_git_review, '-d', change_id)