From 11b1f372c6df886c8eaa806a8032569da11ee261 Mon Sep 17 00:00:00 2001
From: William Manley <will@williammanley.net>
Date: Fri, 22 Jun 2018 11:37:37 +0100
Subject: [PATCH 1/3] OstreeMutableTree: Document each private member of
 `OstreeMutableTree`
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A prelude to my understanding.  Unfortunately `OstreeMutableTree` provides
little encapsulation, as each member has setters† so it's difficult to come
up with a list of invariants.

† `files` and `subdirs` only have getters, but the getters return mutable
  references to the internals, so we still can't reason about invariants.
---
 src/libostree/ostree-mutable-tree.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/libostree/ostree-mutable-tree.c b/src/libostree/ostree-mutable-tree.c
index 5cff5d82bd..f46e36dbe4 100644
--- a/src/libostree/ostree-mutable-tree.c
+++ b/src/libostree/ostree-mutable-tree.c
@@ -47,10 +47,20 @@ struct OstreeMutableTree
 {
   GObject parent_instance;
 
+  /* This is the checksum of the Dirtree object that corresponds to the current
+   * contents of this directory.  contents_checksum can be NULL if the SHA was
+   * never calculated or contents of the mtree has been modified.  Even if
+   * contents_checksum is not NULL it may be out of date. */
   char *contents_checksum;
+
+  /* This is the checksum of the DirMeta object that holds the uid, gid, mode
+   * and xattrs of this directory.  This can be NULL. */
   char *metadata_checksum;
 
+  /* const char* filename -> const char* checksum */
   GHashTable *files;
+
+  /* const char* filename -> OstreeMutableTree* subtree */
   GHashTable *subdirs;
 };
 

From 48f64451c5e381056cb9d220b47eb685be86852d Mon Sep 17 00:00:00 2001
From: William Manley <will@williammanley.net>
Date: Fri, 22 Jun 2018 12:00:29 +0100
Subject: [PATCH 2/3] OstreeMutableTree: Document
 ostree_mutable_tree_ensure_dir

---
 src/libostree/ostree-mutable-tree.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/libostree/ostree-mutable-tree.c b/src/libostree/ostree-mutable-tree.c
index f46e36dbe4..e5e282d4d0 100644
--- a/src/libostree/ostree-mutable-tree.c
+++ b/src/libostree/ostree-mutable-tree.c
@@ -186,6 +186,16 @@ ostree_mutable_tree_replace_file (OstreeMutableTree *self,
   return ret;
 }
 
+/**
+ * ostree_mutable_tree_ensure_dir:
+ * @self: Tree
+ * @name: Name of subdirectory of self to retrieve/creates
+ * @out_subdir: (out) (transfer full): the subdirectory
+ * @error: a #GError
+ *
+ * Returns the subdirectory of self with filename @name, creating an empty one
+ * it if it doesn't exist.
+ */
 gboolean
 ostree_mutable_tree_ensure_dir (OstreeMutableTree *self,
                                 const char        *name,

From 36f7a6d18267814b4d11cb5a89e2ed7993b3d543 Mon Sep 17 00:00:00 2001
From: William Manley <will@williammanley.net>
Date: Sat, 23 Jun 2018 13:11:07 +0100
Subject: [PATCH 3/3] Add test for composing trees in different ways

In preparation for adding `ostree commit` optimisations.
---
 tests/basic-test.sh | 48 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/tests/basic-test.sh b/tests/basic-test.sh
index e0ed2c3233..a0c2f1f763 100644
--- a/tests/basic-test.sh
+++ b/tests/basic-test.sh
@@ -435,6 +435,54 @@ $OSTREE checkout test3-combined checkout-test3-combined
 assert_has_file checkout-test3-combined/file-a
 assert_has_file checkout-test3-combined/file-b
 
+mkdir -p tree-C/usr/share tree-C/usr/bin tree-C/etc tree-D/etc
+
+echo exe >tree-C/usr/bin/exe
+echo sudoers1 >tree-C/etc/sudoers
+echo mtab >tree-C/etc/mtab
+
+echo sudoers2 >tree-D/etc/sudoers
+
+$OSTREE commit ${COMMIT_ARGS} -b test3-C1 --tree=dir=tree-C
+$OSTREE commit ${COMMIT_ARGS} -b test3-D --tree=dir=tree-D
+
+echo sudoers2 >tree-C/etc/sudoers
+$OSTREE commit ${COMMIT_ARGS} -b test3-C2 --tree=dir=tree-C
+echo sudoers1 >tree-C/etc/sudoers
+
+$OSTREE commit ${COMMIT_ARGS} -b test3-ref-ref --tree=ref=test3-C1 --tree=ref=test3-D
+$OSTREE commit ${COMMIT_ARGS} -b test3-dir-ref --tree=dir=tree-C --tree=ref=test3-D
+$OSTREE commit ${COMMIT_ARGS} -b test3-ref-dir --tree=ref=test3-C1 --tree=dir=tree-D
+$OSTREE commit ${COMMIT_ARGS} -b test3-dir-dir --tree=dir=tree-C --tree=dir=tree-D
+
+assert_trees_identical() {
+    $OSTREE diff "$1" "$2" > "diff-$1-$2"
+    cat "diff-$1-$2" 1>&2
+    assert_file_empty "diff-$1-$2"
+    rm "diff-$1-$2"
+}
+
+for x in ref dir
+do
+    for y in ref dir
+    do
+        assert_trees_identical test3-C2 "test3-$x-$y"
+    done
+done
+
+# Regression test
+
+mkdir -p tree-E/etc
+mkdir -p tree-F/etc/apt/sources.list.d/
+echo contents >tree-F/etc/apt/sources.list.d/universe.list
+
+$OSTREE commit ${COMMIT_ARGS} -b test3-E --tree=dir=tree-E
+$OSTREE commit ${COMMIT_ARGS} -b test3-F --tree=dir=tree-F
+
+$OSTREE commit ${COMMIT_ARGS} -b test3-F2 --tree=ref=test3-E --tree=ref=test3-F
+
+assert_trees_identical test3-F test3-F2
+
 echo "ok commit combined ref trees"
 
 # NB: The + is optional, but we need to make sure we support it