Correct common spelling mistakes in comments and tests

Most of these were found using Lucas De Marchi's codespell tool.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Acked-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/diff.c b/diff.c
index db952a5..0eb2653 100644
--- a/diff.c
+++ b/diff.c
@@ -1565,7 +1565,7 @@
 	 * Binary files are displayed with "Bin XXX -> YYY bytes"
 	 * instead of the change count and graph. This part is treated
 	 * similarly to the graph part, except that it is not
-	 * "scaled". If total width is too small to accomodate the
+	 * "scaled". If total width is too small to accommodate the
 	 * guaranteed minimum width of the filename part and the
 	 * separators and this message, this message will "overflow"
 	 * making the line longer than the maximum width.