Preserve trailing newlines during rebase

Bash likes to remove these, which meant the metadata that went inside
the new commit didn't actually match the file it was read from.

apertis-issues#170



Signed-off-by: Ryan Gonzalez <ryan.gonzalez@collabora.com>

generate_pipeline.py

@@ -79,7 +79,9 @@ for ref in $refs; do
             message=$(ostree show "$prev" \\
                         | grep '^ ' \\
                         | sed 's/^ *//g')
-            metadata=$(ostree cat "$prev" metadata)
+            # Trick to preserve any trailing newlines:
+            # https://unix.stackexchange.com/a/383411/117660
+            IFS= read -rd '' metadata < <(ostree cat "$prev" metadata)
 
             echo 'Applying new changes on top of remote...'
             ostree commit -b "$ref" -m "$message" \\

tests/test_build_pipelines.py

@@ -497,6 +497,10 @@ def test_subsummaries_flatpak_metadata(subsummaries):
 
         for ref, (_commit_size, _commit_checksum, ref_metadata) in refs:
             flatpak_metadata = ref_metadata['xa.data'][2]
+            # The metadata file should have a single trailing newline.
+            assert flatpak_metadata.endswith('\n')
+            assert not flatpak_metadata.endswith('\n\n')
+
             keyfile = GLib.KeyFile.new()
             keyfile.load_from_bytes(GLib.Bytes.new(flatpak_metadata.encode('ascii')), 0)