read-cache: fix index corruption with index v4

diff --git a/contrib/rerere-train.sh b/contrib/rerere-train.sh
index 52ad9e41fb7aba37abf71dad2bf5a0015b01dca7..eeee45dd341b25d51b7497c4def555c4133c4267 100755 (executable)
--- a/contrib/rerere-train.sh
+++ b/contrib/rerere-train.sh
@@ -3,10 +3,56 @@
 # Prime rerere database from existing merge commits
 
 me=rerere-train
-USAGE="$me rev-list-args"
+USAGE=$(cat <<-EOF
+usage: $me [--overwrite] <rev-list-args>
+
+    -h, --help            show the help
+    -o, --overwrite       overwrite any existing rerere cache
+EOF
+)
 
 SUBDIRECTORY_OK=Yes
-OPTIONS_SPEC=
+
+overwrite=0
+
+while test $# -gt 0
+do
+       opt="$1"
+       case "$opt" in
+       -h|--help)
+               echo "$USAGE"
+               exit 0
+               ;;
+       -o|--overwrite)
+               overwrite=1
+               shift
+               break
+               ;;
+       --)
+               shift
+               break
+               ;;
+       *)
+               break
+               ;;
+       esac
+done
+
+# Overwrite or help options are not valid except as first arg
+for opt in "$@"
+do
+       case "$opt" in
+       -h|--help)
+               echo "$USAGE"
+               exit 0
+               ;;
+       -o|--overwrite)
+               echo "$USAGE"
+               exit 0
+               ;;
+       esac
+done
+
 . "$(git --exec-path)/git-sh-setup"
 require_work_tree
 cd_to_toplevel
@@ -34,6 +80,10 @@ do
                # Cleanly merges
                continue
        fi
+       if test $overwrite = 1
+       then
+               git rerere forget .
+       fi
        if test -s "$GIT_DIR/MERGE_RR"
        then
                git show -s --pretty=format:"Learning from %h %s" "$commit"