diff: reset color before printing newline

It worked that way since commit 50f575f (Tweak diff colors,
2006-06-22), but commit c1795bb (Unify whitespace checking, 2007-12-13)
changed it.  This patch restores the old behaviour.

Besides Linus' arguments in the log message of 50f575f, resetting color
before printing newline is also important to keep 'git add --patch'
happy.  If the last line(s) of a file are removed, then that hunk will
end with a colored line.  However, if the newline comes before the color
reset, then the diff output will have an additional line at the end
containing only the reset sequence.  This causes trouble in
git-add--interactive.perl's parse_diff function, because @colored will
have one more element than @diff, and that last element will contain the
color reset.  The elements of these arrays will then be copied to @hunk,
but only as many as the number of elements in @diff.  As a result the
last color reset is lost and all subsequent terminal output will be
printed in color.

Signed-off-by: SZEDER Gábor <szeder@ira.uka.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff.c

@@ -514,9 +514,13 @@ const char *diff_get_color(int diff_use_color, enum color_diff ix)
 
 static void emit_line(FILE *file, const char *set, const char *reset, const char *line, int len)
 {
+	if (len > 0 && line[len-1] == '\n')
+		len--;
+
 	fputs(set, file);
 	fwrite(line, len, 1, file);
 	fputs(reset, file);
+	fputc('\n', file);
 }
 
 static void emit_add_line(const char *reset, struct emit_callback *ecbdata, const char *line, int len)