Add function to read all entries in a group

Use that to extend xdg-desktop-read-file.  Also fix a bug where all
entries in all groups were read and returned by xdg-desktop-read-file.
* lisp/xdg.el (xdg-desktop-read-group): New function.
(xdg-desktop-read-file): Use it.
* test/data/xdg/malformed.desktop: New file.
* test/data/xdg/test.desktop: Add another section.
* test/lisp/xdg-tests.el (xdg-desktop-parsing): Test presence of a key
in another group.  Test reading a prescribed group.  Test detecting a
malformed key=value.

2 files changed, 6 insertions, 0 deletions

diff --git a/test/data/xdg/malformed.desktop b/test/data/xdg/malformed.desktop
new file mode 100644
index 00000000000..144a3f719d5
--- /dev/null
+++ b/test/data/xdg/malformed.desktop
@@ -0,0 +1,4 @@
+# unacceptable key=value format
+[Desktop Entry]
+Key=value
+aowef faoweif of
diff --git a/test/data/xdg/test.desktop b/test/data/xdg/test.desktop
index b6dda62774a..b848cef5b0f 100644
--- a/test/data/xdg/test.desktop
+++ b/test/data/xdg/test.desktop
@@ -1,3 +1,5 @@
 # this is a comment
 [Desktop Entry]
 Name=Test
+[Another Section]
+Exec=frobnicate