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

Merge commit '1b593e1ea4' as 'third_party/git'

third_party/git/t/t9150/make-svk-dump

@@ -0,0 +1,57 @@
+#!/bin/sh
+#
+# this script sets up a Subversion repository for Makefile in the
+# first ever git merge, as if it were done with svk.
+#
+
+set -e
+
+svk depotmap foo ~/.svk/foo
+svk co /foo/ foo
+cd foo
+mkdir trunk
+mkdir branches
+svk add trunk branches
+svk commit -m "Setup trunk and branches"
+cd trunk
+
+git cat-file blob 6683463e:Makefile > Makefile
+svk add Makefile 
+
+svk commit -m "ancestor"
+cd ..
+svk cp trunk branches/left
+
+svk commit -m "make left branch"
+cd branches/left/
+
+git cat-file blob 5873b67e:Makefile > Makefile
+svk commit -m "left update 1"
+
+cd ../../trunk
+git cat-file blob 75118b13:Makefile > Makefile
+svk commit -m "trunk update"
+
+cd ../branches/left
+git cat-file blob b5039db6:Makefile > Makefile
+svk commit -m "left update 2"
+
+cd ../../trunk
+svk sm /foo/branches/left
+# in theory we could delete the "left" branch here, but it's not
+# required so don't do it, in case people start getting ideas ;)
+svk commit -m "merge branch 'left' into 'trunk'"
+
+git cat-file blob b51ad431:Makefile > Makefile
+
+svk diff Makefile && echo "Hey!  No differences, magic"
+
+cd ../..
+
+svnadmin dump ~/.svk/foo > svk-merge.dump
+
+svk co -d foo
+rm -rf foo
+svk depotmap -d /foo/
+rm -rf ~/.svk/foo
+