git/cheat-sheet.md: Add explicit push branch and document branch base

Pulls in:
* d97debc cheat-sheet.md: Mention the default root for 'git branch ...'
* 7af9993 cheat-sheet.md: Explicitly list the branch to push

diff --git a/git b/git
index 69d18426ef42d6b1bb4518012edffda4c0a7f812..d97debc2d98304277e0ad69ec91ccc92dea62a63 160000 (submodule)
--- a/git
+++ b/git
@@ -1 +1 @@
-Subproject commit 69d18426ef42d6b1bb4518012edffda4c0a7f812
+Subproject commit d97debc2d98304277e0ad69ec91ccc92dea62a63