(fix)capture: fill-template preserve whitespace content (#2117)

* (fix)capture: fill-template preserve whitespace content

Preserve the whitespace content given in the capture template, by
caching it and then appending it to the output template. For
Org-capture's purposes, we need to separately ensure that a newline is
present. Adds tests to the various helper functions to illustrate changes.

Addresses #2115

tests/test-org-roam-utils.el

@@ -0,0 +1,39 @@
+;;; test-org-roam-utils.el --- Tests for Org-roam -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2020 Jethro Kuan
+
+;; Author: Jethro Kuan <jethrokuan95@gmail.com>
+;; Package-Requires: ((buttercup))
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+;;; Code:
+
+(require 'buttercup)
+(require 'org-roam)
+
+(describe "org-roam-whitespace-content"
+  (it "extracts whitespace correctly"
+    (expect
+     (org-roam-whitespace-content "foo")
+     :to-equal "")
+    (expect
+     (org-roam-whitespace-content "foo\n")
+     :to-equal "\n")
+    (expect
+     (org-roam-whitespace-content "foo\n\t\n")
+     :to-equal "\n\t\n")))
+
+(provide 'test-org-roam-utils)