Merge branch 'maint'

* maint:
  Documentation: bisect: change a few instances of "git-cmd" to "git cmd"
  Documentation: rev-list: change a few instances of "git-cmd" to "git cmd"
  checkout: Don't crash when switching away from an invalid branch.

t/t2011-checkout-invalid-head.sh

@@ -0,0 +1,18 @@
+#!/bin/sh
+
+test_description='checkout switching away from an invalid branch'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	echo hello >world &&
+	git add world &&
+	git commit -m initial
+'
+
+test_expect_success 'checkout master from invalid HEAD' '
+	echo 0000000000000000000000000000000000000000 >.git/HEAD &&
+	git checkout master --
+'
+
+test_done