[PATCH] git-diff: complain about >=8 consecutive spaces in initial indent

[Junio C Hamano <gitster@pobox.com>]

This teaches coloring code in "diff" to detect indent of 8 or
more places using SP, which can and should (in some projects
including the kernel and git itself) use HT instead.

---

 * This is primarily meant as a "reminder" patch, and not for
   inclusion.  We earlier saw a patch to "git-apply" to rewrite
   them to HT but rejected it, because some projects use "no HT,
   all SP" policy (e.g. Python).

   We probably should resurrect the earlier "git-apply" patch,
   and teach it and this patch to selectively enable/disable
   detection of different kinds of whitespace breakages.

 diff.c |   11 +++++++++--
 1 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/diff.c b/diff.c
index 0ee9ea1..647377b 100644
--- a/diff.c
+++ b/diff.c
@@ -531,8 +531,10 @@ static void emit_line_with_ws(int nparents,
 	int i;
 	int tail = len;
 	int need_highlight_leading_space = 0;
-	/* The line is a newly added line.  Does it have funny leading
-	 * whitespaces?  In indent, SP should never precede a TAB.
+	/*
+	 * The line is a newly added line.  Does it have funny leading
+	 * whitespaces?  In indent, SP should never precede a TAB, and
+	 * there shouldn't be more than 8 consecutive spaces.
 	 */
 	for (i = col0; i < len; i++) {
 		if (line[i] == '\t') {
@@ -545,6 +547,11 @@ static void emit_line_with_ws(int nparents,
 		else
 			break;
 	}
+	if (0 <= last_space_in_indent && last_tab_in_indent < 0 &&
+	    8 <= (i - col0)) {
+		last_tab_in_indent = i;
+		need_highlight_leading_space = 1;
+	}
 	fputs(set, stdout);
 	fwrite(line, col0, 1, stdout);
 	fputs(reset, stdout);