Merge branch 'upgrade_git' into 'master'

Update git to 2.8.4.

I've checked [all release notes](https://github.com/git/git/tree/master/Documentation/RelNotes) between the two versions and nothing in there stood out as a breaking change.
This is safe to merge pending an internal event. It can be postponed to 8.15.

cc @gitlab-build-team

See merge request !1108

CHANGELOG.md

@@ -3,6 +3,10 @@
 The latest version of this file can be found at the master branch of the
 omnibus-gitlab repository.
 
+8.15.0
+
+- Update git to 2.8.4
+
 8.14.0
 
 - Switch the redis user's shell to /bin/false 9d60ee4

config/software/git.rb

@@ -17,7 +17,7 @@
 #
 
 name "git"
-default_version "2.7.4"
+default_version "2.8.4"
 
 license "GPL-2.0"
 license_file "COPYING"
@@ -26,8 +26,8 @@ dependency "zlib"
 dependency "openssl"
 dependency "curl"
 
-source :url => "https://www.kernel.org/pub/software/scm/git/git-#{version}.tar.gz",
-       :md5 => "c64012d491e24c7d65cd389f75383d91"
+source url: "https://www.kernel.org/pub/software/scm/git/git-#{version}.tar.gz",
+       sha256: "626e319f8a24fc0866167ea5f6bf3e2f38f69d6cb2e59e150f13709ca3ebf301"
 
 relative_path "git-#{version}"