Merge branch 'am/doc-sha256'

Tone down the warning on SHA-256 repositories being an experimental
curiosity.  We do not have support for them to interoperate with
traditional SHA-1 repositories, but at this point, we do not plan
to make breaking changes to SHA-256 repositories and there is no
longer need for such a strongly phrased warning.

* am/doc-sha256:
  doc: sha256 is no longer experimental

Documentation/git.txt

@@ -553,8 +553,8 @@ double-quotes and respecting backslash escapes. E.g., the value
 	If this variable is set, the default hash algorithm for new
 	repositories will be set to this value. This value is
 	ignored when cloning and the setting of the remote repository
-	is always used. The default is "sha1". THIS VARIABLE IS
-	EXPERIMENTAL! See `--object-format` in linkgit:git-init[1].
+	is always used. The default is "sha1".
+	See `--object-format` in linkgit:git-init[1].
 
 Git Commits
 ~~~~~~~~~~~

Documentation/object-format-disclaimer.txt

@@ -1,6 +1,9 @@
-THIS OPTION IS EXPERIMENTAL! SHA-256 support is experimental and still
-in an early stage.  A SHA-256 repository will in general not be able to
-share work with "regular" SHA-1 repositories.  It should be assumed
-that, e.g., Git internal file formats in relation to SHA-256
-repositories may change in backwards-incompatible ways.  Only use
-`--object-format=sha256` for testing purposes.
+Note: At present, there is no interoperability between SHA-256
+repositories and SHA-1 repositories.
+
+Historically, we warned that SHA-256 repositories may later need
+backward incompatible changes when we introduce such interoperability
+features. Today, we only expect compatible changes. Furthermore, if such
+changes prove to be necessary, it can be expected that SHA-256 repositories
+created with today's Git will be usable by future versions of Git
+without data loss.