Added new section to the git-svn getting started section that provides a

custom git script called git-svnup which handles all of the work of
using the git-mirrors/keeping the git-svn numbers in sync.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173472 91177308-0d34-0410-b5e6-96231b3b80d8

docs/GettingStarted.rst

@@ -639,6 +639,34 @@ This leaves your working directories on their master branches, so you'll need to
 ``checkout`` each working branch individually and ``rebase`` it on top of its
 parent branch.
 
+For those who wish to be able to update an llvm repo in a simpler fashion,
+consider placing the following git script in your path under the name
+``git-svnup``:
+
+.. code-block:: bash
+
+  #!/bin/bash
+
+  STATUS=$(git status -s | grep -v "??")
+
+  if [ ! -z "$STATUS" ]; then
+      STASH="yes"
+      git stash >/dev/null
+  fi
+
+  git fetch
+  old_branch=$(git rev-parse --abbrev-ref HEAD)
+  git checkout master 2> /dev/null
+  git svn rebase -l
+  git checkout $old_breanch 2> /dev/null
+
+  if [ ! -z $STASH ]; then
+      git stash pop >/dev/null
+  fi
+
+Then to perform the aforementioned update steps go into your source directory
+and just type ``git-svnup`` or ``git svnup`` and everything will just work.
+
 To commit back changes via git-svn, use ``dcommit``:
 
 .. code-block:: console