gc docs: re-flow the "gc.*" section in "config"

diff --git a/Documentation/config/diff.txt b/Documentation/config/diff.txt
index e4db77bc82dfc2576cf02ae392407a0df0728686..e48bb987d789e033e1da012a7f950177848b5b23 100644 (file)
--- a/Documentation/config/diff.txt
+++ b/Documentation/config/diff.txt
@@ -177,6 +177,14 @@ diff.tool::
        Any other value is treated as a custom diff tool and requires
        that a corresponding difftool.<tool>.cmd variable is defined.
 
+diff.guitool::
+       Controls which diff tool is used by linkgit:git-difftool[1] when
+       the -g/--gui flag is specified. This variable overrides the value
+       configured in `merge.guitool`. The list below shows the valid
+       built-in values. Any other value is treated as a custom diff tool
+       and requires that a corresponding difftool.<guitool>.cmd variable
+       is defined.
+
 include::../mergetools-diff.txt[]
 
 diff.indentHeuristic::