[gimp] .gitlab: adding a MR template.

[Jehan <jehanp src gnome org>]

commit 590b8bb4bf29e6b8dfdb2cd6d4f1d6db4108c021
Author: Jehan <jehan girinstud io>
Date:   Tue Jun 26 20:47:00 2018 +0200

    .gitlab: adding a MR template.
    
    This is not really a template, more like recommendations so that we
    don't have to repeat ourselves too much (hopefully). Let's hope it
    helps.

 .gitlab/merge_request_templates/default.md | 7 +++++++
 1 file changed, 7 insertions(+)
---
diff --git a/.gitlab/merge_request_templates/default.md b/.gitlab/merge_request_templates/default.md
new file mode 100644
index 0000000000..71203d7299
--- /dev/null
+++ b/.gitlab/merge_request_templates/default.md
@@ -0,0 +1,7 @@
+Please follow our coding style, which is mostly the GNU coding style
+with some specificities: see [HACKING](HACKING#L123).
+
+Also make sure no trailing spaces or tabs are left out.
+
+Finally please check the following option when making your request:
+"*Allow commits from members who can merge to the target branch.*"