log: Update log.follow doc and add to config.txt

Documentation/config.txt does not include the documentation for
log.follow that is in Documentation/git-log.txt.  This commit adds the
log.follow documentation to config.txt and also updates the wording to
be consistent with the format that is followed by other boolean
configuration variables.

Signed-off-by: Eric N. Vander Weele <ericvw@gmail.com>
Acked-by: David Turner <dturner@twopensource.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -1792,6 +1792,12 @@ log.decorate::
 	specified, the full ref name (including prefix) will be printed.
 	This is the same as the log commands '--decorate' option.
 
+log.follow::
+	If `true`, `git log` will act as if the `--follow` option was used when
+	a single <path> is given.  This has the same limitations as `--follow`,
+	i.e. it cannot be used to follow multiple files and does not work well
+	on non-linear history.
+
 log.showRoot::
 	If true, the initial commit will be shown as a big creation event.
 	This is equivalent to a diff against an empty tree.

Documentation/git-log.txt

@@ -185,10 +185,10 @@ log.date::
 	dates like `Sat May 8 19:35:34 2010 -0500`.
 
 log.follow::
-	If a single <path> is given to git log, it will act as
-	if the `--follow` option was also used.  This has the same
-	limitations as `--follow`, i.e. it cannot be used to follow
-	multiple files and does not work well on non-linear history.
+	If `true`, `git log` will act as if the `--follow` option was used when
+	a single <path> is given.  This has the same limitations as `--follow`,
+	i.e. it cannot be used to follow multiple files and does not work well
+	on non-linear history.
 
 log.showRoot::
 	If `false`, `git log` and related commands will not treat the