Git-prune-script loses blobs referenced from an uncommitted cache.

(updated from the version posted to GIT mailing list).

When a new blob is registered with update-cache, and before the cache
is written as a tree and committed, git-fsck-cache will find the blob
unreachable.  This patch adds a new flag, "--cache" to git-fsck-cache,
with which it keeps such blobs from considered "unreachable".

The git-prune-script is updated to use this new flag.  At the same time
it adds .git/refs/*/* to the set of default locations to look for heads,
which should be consistent with expectations from Cogito users.

Without this fix, "diff-cache -p --cached" after git-prune-script has
pruned the blob object will fail mysteriously and git-write-tree would
also fail.

Signed-off-by: Junio C Hamano <junkio@cox.net>

git-prune-script

@@ -1,2 +1,37 @@
 #!/bin/sh
-git-fsck-cache --unreachable $(cat .git/HEAD ) | grep unreachable | cut -d' ' -f3 | sed 's:^\(..\):.git/objects/\1/:' | xargs rm
+
+dryrun=
+while case "$#" in 0) break ;; esac
+do
+    case "$1" in
+    -n) dryrun=echo ;;
+    --) break ;;
+    -*) echo >&2 "usage: git-prune-script [ -n ] [ heads... ]"; exit 1 ;;
+    *)  break ;;
+    esac
+    shift;
+done
+
+# Defaulting to include .git/refs/*/* may be debatable from the
+# purist POV but power users can always give explicit parameters
+# to the script anyway.
+
+case "$#" in
+0)
+    x_40='[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]'
+    x_40="$x_40$x_40$x_40$x_40$x_40$x_40$x_40$x_40"
+    set x $(sed -ne "/^$x_40\$/p" .git/HEAD .git/refs/*/* 2>/dev/null)
+    shift ;;
+esac
+
+git-fsck-cache --cache --unreachable "$@" |
+sed -ne '/unreachable /{
+    s/unreachable [^ ][^ ]* //
+    s|\(..\)|\1/|p
+}' | {
+	case "$SHA1_FILE_DIRECTORY" in
+	'') cd .git/objects/ ;;
+	*) cd "$SHA1_FILE_DIRECTORY" ;;
+	esac || exit
+	xargs -r $dryrun rm -f
+}