taskwarrior: patch bug in bash-completion file

The patch was submitted upstream, too.

pkgs/applications/misc/taskwarrior/0001-bash-completion-quote-pattern-argument-to-grep.patch

···
+From 0d677475b710b9bb61d4b3ac5435c36b47d3a155 Mon Sep 17 00:00:00 2001
+From: Peter Simons <[e-mail]>
+Date: Wed, 8 Feb 2017 11:28:42 +0100
+Subject: [PATCH] bash-completion: quote pattern argument to grep
+
+Without the quotes, bash might expand that pattern based on the contents of the
+current working directory or -- if nullglob is set -- the argument disappears
+outright if no directory entry matches.
+---
+ scripts/bash/task.sh | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/scripts/bash/task.sh b/scripts/bash/task.sh
+index e0c7fb03..d15ed3eb 100644
+--- a/scripts/bash/task.sh
++++ b/scripts/bash/task.sh
+@@ -72,7 +72,7 @@ _task_offer_contexts() {
+     COMPREPLY=( $(compgen -W "$($taskcommand _context) define delete list none show" -- $cur) )
+ }
+ 
+-_task_context_alias=$($taskcommand show | grep alias.*context | cut -d' ' -f1 | cut -d. -f2)
++_task_context_alias=$($taskcommand show | grep "alias.*context" | cut -d' ' -f1 | cut -d. -f2)
+ 
+ _task()
+ {
+-- 
+2.11.1
+

pkgs/applications/misc/taskwarrior/default.nix

···
     sha256 = "059a9yc58wcicc6xxsjh1ph7k2yrag0spsahp1wqmsq6h7jwwyyq";
   };
 
+  patches = [ ./0001-bash-completion-quote-pattern-argument-to-grep.patch ];
+
   nativeBuildInputs = [ cmake libuuid gnutls ];
 
   postInstall = ''