mesa: simplify get-pick-list.sh script

and add a description for the script

NOTE: This is a candidate for the stable branches.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

bin/get-pick-list.sh

@@ -1,6 +1,8 @@
 #!/bin/sh
 
-git log --reverse --pretty=oneline HEAD..origin/master | cut -d' ' -f1 |\
+# Script for generating a list of candidates for cherry-picking to a stable branch
+
+git log --reverse --pretty=%H HEAD..origin/master |\
 while read sha
 do
     # Check to see whether the patch was marked as a candidate for the stable tree.