Merge branch 'cb/bash-completion-ls-files-processing' into next

Shell completion (in contrib) that gives list of paths have been
optimized somewhat.

* cb/bash-completion-ls-files-processing:
  completion: improve ls-files filter performance

This fixes git-for-windows#1533

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

contrib/completion/git-completion.bash

@@ -388,12 +388,7 @@ __git_index_files ()
 	local root="${2-.}" file
 
 	__git_ls_files_helper "$root" "$1" |
-	while read -r file; do
-		case "$file" in
-		?*/*) echo "${file%%/*}" ;;
-		*) echo "$file" ;;
-		esac
-	done | sort | uniq
+	cut -f1 -d/ | sort | uniq
 }
 
 # Lists branches from the local repository.