Documentation: use proper wording for ref format strings

Various commands list refs and allow to use a format string for the
output that interpolates from the ref as well as the object it points
at (for-each-ref; branch and tag in list mode).

Currently, the documentation talks about interpolating from the object.
This is confusing because a ref points to an object but not vice versa,
so the object cannot possible know %(refname), for example. Thus, this is
wrong independent of refs being objects (one day, maybe) or not.

Change the wording to make this clearer (and distinguish it from formats
for the log family).

Signed-off-by: Michael J Gruber <git@grubix.eu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-branch.txt

@@ -267,8 +267,8 @@ start-point is either a local or remote-tracking branch.
 	Only list branches of the given object.
 
 --format <format>::
-	A string that interpolates `%(fieldname)` from the object
-	pointed at by a ref being shown.  The format is the same as
+	A string that interpolates `%(fieldname)` from a branch ref being shown
+	and the object it points at.  The format is the same as
 	that of linkgit:git-for-each-ref[1].
 
 Examples

Documentation/git-for-each-ref.txt

@@ -38,8 +38,8 @@ OPTIONS
 	key.
 
 <format>::
-	A string that interpolates `%(fieldname)` from the
-	object pointed at by a ref being shown.  If `fieldname`
+	A string that interpolates `%(fieldname)` from a ref being shown
+	and the object it points at.  If `fieldname`
 	is prefixed with an asterisk (`*`) and the ref points
 	at a tag object, the value for the field in the object
 	tag refers is used.  When unspecified, defaults to

Documentation/git-tag.txt

@@ -188,8 +188,8 @@ This option is only applicable when listing tags without annotation lines.
 	Defaults to HEAD.
 
 <format>::
-	A string that interpolates `%(fieldname)` from the object
-	pointed at by a ref being shown.  The format is the same as
+	A string that interpolates `%(fieldname)` from a tag ref being shown
+	and the object it points at.  The format is the same as
 	that of linkgit:git-for-each-ref[1].  When unspecified,
 	defaults to `%(refname:strip=2)`.