[PATCH 4/6] Improve error message for git-filter-branch

[John Tapsell <johnflux@gmail.com>]

Tell the user that a backup (original) already exists, and how to solve
this problem (with -f option)
---
 git-filter-branch.sh |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/git-filter-branch.sh b/git-filter-branch.sh
index 27b57b8..1ca45e2 100755
--- a/git-filter-branch.sh
+++ b/git-filter-branch.sh
@@ -226,7 +226,8 @@ while read sha1 type name
 do
 	case "$force,$name" in
 	,$orig_namespace*)
-		die "Namespace $orig_namespace not empty"
+		die "Cannot backup - a previous backup already exists in $orig_namespace\n" \
+		    "Force overwriting the backup with -f"
 	;;
 	t,$orig_namespace*)
 		git update-ref -d "$name" $sha1
-- 
1.6.2.rc1.3.g7d31b.dirty