Merge branch 'tr/notes-display'

* tr/notes-display:
  git-notes(1): add a section about the meaning of history
  notes: track whether notes_trees were changed at all
  notes: add shorthand --ref to override GIT_NOTES_REF
  commit --amend: copy notes to the new commit
  rebase: support automatic notes copying
  notes: implement helpers needed for note copying during rewrite
  notes: implement 'git notes copy --stdin'
  rebase -i: invoke post-rewrite hook
  rebase: invoke post-rewrite hook
  commit --amend: invoke post-rewrite hook
  Documentation: document post-rewrite hook
  Support showing notes from more than one notes tree
  test-lib: unset GIT_NOTES_REF to stop it from influencing tests

Conflicts:
	git-am.sh
	refs.c

git-am.sh

@@ -593,6 +593,7 @@ do
 			echo "Patch is empty.  Was it split wrong?"
 			stop_here $this
 		}
+		rm -f "$dotest/original-commit"
 		if test -f "$dotest/rebasing" &&
 			commit=$(sed -e 's/^From \([0-9a-f]*\) .*/\1/' \
 				-e q "$dotest/$msgnum") &&
@@ -600,6 +601,7 @@ do
 		then
 			git cat-file commit "$commit" |
 			sed -e '1,/^$/d' >"$dotest/msg-clean"
+			echo "$commit" > "$dotest/original-commit"
 		else
 			{
 				sed -n '/^Subject/ s/Subject: //p' "$dotest/info"
@@ -783,6 +785,10 @@ do
 	git update-ref -m "$GIT_REFLOG_ACTION: $FIRSTLINE" HEAD $commit $parent ||
 	stop_here $this
 
+	if test -f "$dotest/original-commit"; then
+		echo "$(cat "$dotest/original-commit") $commit" >> "$dotest/rewritten"
+	fi
+
 	if test -x "$GIT_DIR"/hooks/post-applypatch
 	then
 		"$GIT_DIR"/hooks/post-applypatch
@@ -791,5 +797,12 @@ do
 	go_next
 done
 
+if test -s "$dotest"/rewritten; then
+    git notes copy --for-rewrite=rebase < "$dotest"/rewritten
+    if test -x "$GIT_DIR"/hooks/post-rewrite; then
+	"$GIT_DIR"/hooks/post-rewrite rebase < "$dotest"/rewritten
+    fi
+fi
+
 rm -fr "$dotest"
 git gc --auto