Fix mismerge at 737049d

The world order after merging the bc/doc-adoc-not-txt topic
is that there is no .txt files in Documentation/ hierarchy,
as everything should have been migrated to .adoc suffix.

There were a fiew topics that were simultaneously in flight
that got graduated earlier than the topic, hence needed an
evil merge to adjust.  This commit belatedly adjusts the merge
result to account for them.  The same merge-fix will be made
when the topic eventually graduates to 'master'.

Reported-by: Jeff King <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: gitster

Documentation/config/difftool.adoc

@@ -13,7 +13,7 @@ diff.guitool::
 	and requires that a corresponding difftool.<guitool>.cmd variable
 	is defined.
 
-include::{build_dir}/mergetools-diff.txt[]
+include::{build_dir}/mergetools-diff.adoc[]
 
 difftool.<tool>.cmd::
 	Specify the command to invoke the specified diff tool.