contrib/git-jump: allow to configure the grep command

index 225e3f095..9f58d5db8 100644
@@ -63,6 +63,9 @@ git jump grep foo_bar
 # same as above, but case-insensitive; you can give
 # arbitrary grep options
 git jump grep -i foo_bar
+
+# use the silver searcher for git jump grep
+git config jump.grepCmd "ag --column"
 --------------------------------------------------
 
 

index 427f206a4..80ab0590b 100755
@@ -11,7 +11,8 @@ diff: elements are diff hunks. Arguments are given to diff.
 
 merge: elements are merge conflicts. Arguments are ignored.
 
-grep: elements are grep hits. Arguments are given to grep.
+grep: elements are grep hits. Arguments are given to git grep or, if
+      configured, to the command in `jump.grepCmd`.
 
 ws: elements are whitespace errors. Arguments are given to diff --check.
 EOF

@@ -50,7 +51,9 @@ mode_merge() {
 # but let's clean up extra whitespace, so they look better if the
 # editor shows them to us in the status bar.
 mode_grep() {
-	git grep -n "$@" |
+	cmd=$(git config jump.grepCmd)
+	test -n "$cmd" || cmd="git grep -n"
+	$cmd "$@" |
 	perl -pe '
 	s/[ \t]+/ /g;
 	s/^ *//;