Add .gitattributes file

The files marked as export-ignore here are not going to be
included in the tarball produced by 'meson dist' when using
meson >= 0.60.

Older versions of meson excluded a small subset of these files
automatically, but since we have more control now we can be
more aggressive and leave out anything that doesn't make sense
in a release tarball.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

.gitattributes

@@ -0,0 +1,22 @@
+# Generic git stuff
+**/.gitattributes export-ignore
+**/.gitignore export-ignore
+/.gitmodules export-ignore
+/.mailmap export-ignore
+
+# Project-specific git stuff
+/.gitpublish export-ignore
+/docs/gitdm export-ignore
+/docs/gitdm/** export-ignore
+/gitdm.config export-ignore
+
+# Code hosting stuff
+/.github export-ignore
+/.github/** export-ignore
+/.gitlab export-ignore
+/.gitlab/** export-ignore
+
+# CI stuff
+/.gitlab-ci.yml export-ignore
+/ci export-ignore
+/ci/** export-ignore