core.whitespace: split trailing-space into blank-at-{eol,eof}

People who configured trailing-space depended on it to catch both extra
white space at the end of line, and extra blank lines at the end of file.
Earlier attempt to introduce only blank-at-eof gave them an escape hatch
to keep the old behaviour, but it is a regression until they explicitly
specify the new error class.

This introduces a blank-at-eol that only catches extra white space at the
end of line, and makes the traditional trailing-space a convenient synonym
to catch both blank-at-eol and blank-at-eof.  This way, people who used
trailing-space continue to catch both classes of errors.

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

Documentation/config.txt

@@ -382,7 +382,7 @@ core.whitespace::
 	consider them as errors.  You can prefix `-` to disable
 	any of them (e.g. `-trailing-space`):
 +
-* `trailing-space` treats trailing whitespaces at the end of the line
+* `blank-at-eol` treats trailing whitespaces at the end of the line
   as an error (enabled by default).
 * `space-before-tab` treats a space character that appears immediately
   before a tab character in the initial indent part of the line as an
@@ -391,6 +391,8 @@ core.whitespace::
   space characters as an error (not enabled by default).
 * `blank-at-eof` treats blank lines added at the end of file as an error
   (enabled by default).
+* `trailing-space` is a short-hand to cover both `blank-at-eol` and
+  `blank-at-eof`.
 * `cr-at-eol` treats a carriage-return at the end of line as
   part of the line terminator, i.e. with it, `trailing-space`
   does not trigger if the character before such a carriage-return

cache.h

@@ -841,12 +841,13 @@ void shift_tree(const unsigned char *, const unsigned char *, unsigned char *, i
  * whitespace rules.
  * used by both diff and apply
  */
-#define WS_TRAILING_SPACE	01
+#define WS_BLANK_AT_EOL         01
 #define WS_SPACE_BEFORE_TAB	02
 #define WS_INDENT_WITH_NON_TAB	04
 #define WS_CR_AT_EOL           010
 #define WS_BLANK_AT_EOF        020
-#define WS_DEFAULT_RULE (WS_TRAILING_SPACE|WS_SPACE_BEFORE_TAB|WS_BLANK_AT_EOF)
+#define WS_TRAILING_SPACE      (WS_BLANK_AT_EOL|WS_BLANK_AT_EOF)
+#define WS_DEFAULT_RULE (WS_TRAILING_SPACE|WS_SPACE_BEFORE_TAB)
 extern unsigned whitespace_rule_cfg;
 extern unsigned whitespace_rule(const char *);
 extern unsigned parse_whitespace_rule(const char *);

ws.c

@@ -15,6 +15,7 @@ static struct whitespace_rule {
 	{ "space-before-tab", WS_SPACE_BEFORE_TAB },
 	{ "indent-with-non-tab", WS_INDENT_WITH_NON_TAB },
 	{ "cr-at-eol", WS_CR_AT_EOL },
+	{ "blank-at-eol", WS_BLANK_AT_EOL },
 	{ "blank-at-eof", WS_BLANK_AT_EOF },
 };
 
@@ -101,9 +102,19 @@ unsigned whitespace_rule(const char *pathname)
 char *whitespace_error_string(unsigned ws)
 {
 	struct strbuf err;
+
 	strbuf_init(&err, 0);
-	if (ws & WS_TRAILING_SPACE)
+	if ((ws & WS_TRAILING_SPACE) == WS_TRAILING_SPACE)
 		strbuf_addstr(&err, "trailing whitespace");
+	else {
+		if (ws & WS_BLANK_AT_EOL)
+			strbuf_addstr(&err, "trailing whitespace");
+		if (ws & WS_BLANK_AT_EOF) {
+			if (err.len)
+				strbuf_addstr(&err, ", ");
+			strbuf_addstr(&err, "new blank line at EOF");
+		}
+	}
 	if (ws & WS_SPACE_BEFORE_TAB) {
 		if (err.len)
 			strbuf_addstr(&err, ", ");
@@ -114,11 +125,6 @@ char *whitespace_error_string(unsigned ws)
 			strbuf_addstr(&err, ", ");
 		strbuf_addstr(&err, "indent with spaces");
 	}
-	if (ws & WS_BLANK_AT_EOF) {
-		if (err.len)
-			strbuf_addstr(&err, ", ");
-		strbuf_addstr(&err, "new blank line at EOF");
-	}
 	return strbuf_detach(&err, NULL);
 }
 
@@ -146,11 +152,11 @@ static unsigned ws_check_emit_1(const char *line, int len, unsigned ws_rule,
 	}
 
 	/* Check for trailing whitespace. */
-	if (ws_rule & WS_TRAILING_SPACE) {
+	if (ws_rule & WS_BLANK_AT_EOL) {
 		for (i = len - 1; i >= 0; i--) {
 			if (isspace(line[i])) {
 				trailing_whitespace = i;
-				result |= WS_TRAILING_SPACE;
+				result |= WS_BLANK_AT_EOL;
 			}
 			else
 				break;
@@ -266,7 +272,7 @@ int ws_fix_copy(char *dst, const char *src, int len, unsigned ws_rule, int *erro
 	/*
 	 * Strip trailing whitespace
 	 */
-	if ((ws_rule & WS_TRAILING_SPACE) &&
+	if ((ws_rule & WS_BLANK_AT_EOL) &&
 	    (2 <= len && isspace(src[len-2]))) {
 		if (src[len - 1] == '\n') {
 			add_nl_to_tail = 1;