core.whitespace: cr-at-eol

This new error mode allows a line to have a carriage return at the
end of the line when checking and fixing trailing whitespace errors.

Some people like to keep CRLF line ending recorded in the repository,
and still want to take advantage of the automated trailing whitespace
stripping.  We still show ^M in the diff output piped to "less" to
remind them that they do have the CR at the end, but these carriage
return characters at the end are no longer flagged as errors.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 13 insertions, 2 deletions

diff --git a/ws.c b/ws.c
index d09b9df89a..5a9ac457db 100644
--- a/ws.c
+++ b/ws.c
@@ -14,6 +14,7 @@ static struct whitespace_rule {
 	{ "trailing-space", WS_TRAILING_SPACE },
 	{ "space-before-tab", WS_SPACE_BEFORE_TAB },
 	{ "indent-with-non-tab", WS_INDENT_WITH_NON_TAB },
+	{ "cr-at-eol", WS_CR_AT_EOL },
 };
 
 unsigned parse_whitespace_rule(const char *string)
@@ -124,6 +125,7 @@ unsigned check_and_emit_line(const char *line, int len, unsigned ws_rule,
 	int written = 0;
 	int trailing_whitespace = -1;
 	int trailing_newline = 0;
+	int trailing_carriage_return = 0;
 	int i;
 
 	/* Logic is simpler if we temporarily ignore the trailing newline. */
@@ -131,6 +133,11 @@ unsigned check_and_emit_line(const char *line, int len, unsigned ws_rule,
 		trailing_newline = 1;
 		len--;
 	}
+	if ((ws_rule & WS_CR_AT_EOL) &&
+	    len > 0 && line[len - 1] == '\r') {
+		trailing_carriage_return = 1;
+		len--;
+	}
 
 	/* Check for trailing whitespace. */
 	if (ws_rule & WS_TRAILING_SPACE) {
@@ -176,8 +183,10 @@ unsigned check_and_emit_line(const char *line, int len, unsigned ws_rule,
 	}
 
 	if (stream) {
-		/* Now the rest of the line starts at written.
-		 * The non-highlighted part ends at trailing_whitespace. */
+		/*
+		 * Now the rest of the line starts at "written".
+		 * The non-highlighted part ends at "trailing_whitespace".
+		 */
 		if (trailing_whitespace == -1)
 			trailing_whitespace = len;
 
@@ -196,6 +205,8 @@ unsigned check_and_emit_line(const char *line, int len, unsigned ws_rule,
 			    len - trailing_whitespace, 1, stream);
 			fputs(reset, stream);
 		}
+		if (trailing_carriage_return)
+			fputc('\r', stream);
 		if (trailing_newline)
 			fputc('\n', stream);
 	}