Add a script to edit/inspect notes

The script 'git notes' allows you to edit and show commit notes, by
calling either

	git notes show <commit>

or

	git notes edit <commit>

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-notes.sh

@@ -0,0 +1,65 @@
+#!/bin/sh
+
+USAGE="(edit | show) [commit]"
+. git-sh-setup
+
+test -n "$3" && usage
+
+test -z "$1" && usage
+ACTION="$1"; shift
+
+test -z "$GIT_NOTES_REF" && GIT_NOTES_REF="$(git config core.notesref)"
+test -z "$GIT_NOTES_REF" && GIT_NOTES_REF="refs/notes/commits"
+
+COMMIT=$(git rev-parse --verify --default HEAD "$@") ||
+die "Invalid commit: $@"
+
+MESSAGE="$GIT_DIR"/new-notes-$COMMIT
+trap '
+	test -f "$MESSAGE" && rm "$MESSAGE"
+' 0
+
+case "$ACTION" in
+edit)
+	GIT_NOTES_REF= git log -1 $COMMIT | sed "s/^/#/" > "$MESSAGE"
+
+	GIT_INDEX_FILE="$MESSAGE".idx
+	export GIT_INDEX_FILE
+
+	CURRENT_HEAD=$(git show-ref "$GIT_NOTES_REF" | cut -f 1 -d ' ')
+	if [ -z "$CURRENT_HEAD" ]; then
+		PARENT=
+	else
+		PARENT="-p $CURRENT_HEAD"
+		git read-tree "$GIT_NOTES_REF" || die "Could not read index"
+		git cat-file blob :$COMMIT >> "$MESSAGE" 2> /dev/null
+	fi
+
+	${VISUAL:-${EDITOR:-vi}} "$MESSAGE"
+
+	grep -v ^# < "$MESSAGE" | git stripspace > "$MESSAGE".processed
+	mv "$MESSAGE".processed "$MESSAGE"
+	if [ -s "$MESSAGE" ]; then
+		BLOB=$(git hash-object -w "$MESSAGE") ||
+			die "Could not write into object database"
+		git update-index --add --cacheinfo 0644 $BLOB $COMMIT ||
+			die "Could not write index"
+	else
+		test -z "$CURRENT_HEAD" &&
+			die "Will not initialise with empty tree"
+		git update-index --force-remove $COMMIT ||
+			die "Could not update index"
+	fi
+
+	TREE=$(git write-tree) || die "Could not write tree"
+	NEW_HEAD=$(echo Annotate $COMMIT | git commit-tree $TREE $PARENT) ||
+		die "Could not annotate"
+	git update-ref -m "Annotate $COMMIT" \
+		"$GIT_NOTES_REF" $NEW_HEAD $CURRENT_HEAD
+;;
+show)
+	git show "$GIT_NOTES_REF":$COMMIT
+;;
+*)
+	usage
+esac