for-each-ref: mark :remote-name and :remote-ref as experimental

These expansions will most likely be introduced into Git for Windows as
a test balloon first, and if they work out as expected, we'll try to get
the patches into upstream Git.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Documentation/git-for-each-ref.txt

@@ -141,9 +141,9 @@ upstream::
 	encountered. Append `:track,nobracket` to show tracking
 	information without brackets (i.e "ahead N, behind M").
 +
-Also respects `:remotename` to state the name of the *remote* instead
-of the ref, and `:remoteref` to state the name of the *reference* as
-locally known by the remote.
+(EXPERIMENTAL) Also respects `:remotename` to state the name of the
+*remote* instead of the ref, and `:remoteref` to state the name of
+the *reference* as locally known by the remote.
 +
 Has no effect if the ref does not have tracking information associated
 with it.  All the options apart from `nobracket` are mutually exclusive,
@@ -152,9 +152,9 @@ but if used together the last option is selected.
 push::
 	The name of a local ref which represents the `@{push}`
 	location for the displayed ref. Respects `:short`, `:lstrip`,
-	`:rstrip`, `:track`, `:trackshort`, `:remotename`, and `:remoteref`
-	options as `upstream` does. Produces an empty string if no `@{push}`
-	ref is configured.
+	`:rstrip`, `:track`, `:trackshort`, (EXPERIMENTAL) `:remotename`,
+	and (EXPERIMENTAL) `:remoteref` options as `upstream` does.
+	Produces an empty string if no `@{push}` ref is configured.
 
 HEAD::
 	'*' if HEAD matches current ref (the checked out branch), ' '