merge(third_party/git): Merge squashed git subtree at v2.23.0

Merge commit '1b593e1ea4' as 'third_party/git'
2020-01-11 23:36:56 +00:00 · 2020-01-11 23:36:56 +00:00 · 7ef0d62730
commit 7ef0d62730
parent 6a2a300707 1b593e1ea4
3629 changed files with 1139935 additions and 0 deletions
--- a/third_party/git/t/t4135/diff-with
+++ b/third_party/git/t/t4135/diff-with
@ -0,0 +1,5 @@
+--- post\image.txt.orig	2010-08-18 20:13:31.680002255 -0500
+++ post\image.txt	2010-08-18 20:13:31.680002255 -0500
+@@ -1 +1 @@
+-preimage
+postimage