Add change 14 to instructions

how_to/Change_14.md

@@ -0,0 +1,31 @@
+- commit: Create commit
+
+So far we were able to save versions of a directory (with `write-tree`), but
+without any additional context. In reality, when we save a snapshot we would
+like to attach data such as:
++ Message describing it
++ When the snapshot was created
++ Who created the snapshot
++ ...
+
+We will create a new type of object called a "commit" that will store all this
+information. A commit will just be a text file stored in the object database
+with the type of `'commit'`.
+
+The first lines in the commit will be key-values, then an empty line will mark
+the end of the key-values and then the commit message will follow. Like this:
+
+```
+tree 5e550586c91fce59e0006799e0d46b3948f05693
+author Nikita Leshenko
+time 2019-09-14T09:31:09+00:00
+
+This is the commit message!
+```
+
+For now we'll just write the "tree" key and the commit message to the commit
+object.
+
+We will create a new `ugit commit` command that will accept a commit message,
+snapshot the current directory using `ugit write-tree` and save the resulting
+object.