Use gitattributes to define per-path whitespace rule

The `core.whitespace` configuration variable allows you to define what
`diff` and `apply` should consider whitespace errors for all paths in
the project (See gitlink:git-config[1]).  This attribute gives you finer
control per path.

For example, if you have these in the .gitattributes:

    frotz   whitespace
    nitfol  -whitespace
    xyzzy   whitespace=-trailing

all types of whitespace problems known to git are noticed in path 'frotz'
(i.e. diff shows them in diff.whitespace color, and apply warns about
them), no whitespace problem is noticed in path 'nitfol', and the
default types of whitespace problems except "trailing whitespace" are
noticed for path 'xyzzy'.  A project with mixed Python and C might want
to have:

    *.c    whitespace
    *.py   whitespace=-indent-with-non-tab

in its toplevel .gitattributes file.

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

1 files changed, 12 insertions, 7 deletions

diff --git a/diff.c b/diff.c
index 6bb902f4a..c3a1942bb 100644
--- a/diff.c
+++ b/diff.c
@@ -454,6 +454,7 @@ static void diff_words_show(struct diff_words_data *diff_words)
 struct emit_callback {
 	struct xdiff_emit_state xm;
 	int nparents, color_diff;
+	unsigned ws_rule;
 	const char **label_path;
 	struct diff_words_data *diff_words;
 	int *found_changesp;
@@ -493,8 +494,8 @@ static void emit_line(const char *set, const char *reset, const char *line, int
 }
 
 static void emit_line_with_ws(int nparents,
-		const char *set, const char *reset, const char *ws,
-		const char *line, int len)
+			      const char *set, const char *reset, const char *ws,
+			      const char *line, int len, unsigned ws_rule)
 {
 	int col0 = nparents;
 	int last_tab_in_indent = -1;
@@ -511,7 +512,7 @@ static void emit_line_with_ws(int nparents,
 	for (i = col0; i < len; i++) {
 		if (line[i] == '\t') {
 			last_tab_in_indent = i;
-			if ((whitespace_rule & WS_SPACE_BEFORE_TAB) &&
+			if ((ws_rule & WS_SPACE_BEFORE_TAB) &&
 			    0 <= last_space_in_indent)
 				need_highlight_leading_space = 1;
 		}
@@ -520,7 +521,7 @@ static void emit_line_with_ws(int nparents,
 		else
 			break;
 	}
-	if ((whitespace_rule & WS_INDENT_WITH_NON_TAB) &&
+	if ((ws_rule & WS_INDENT_WITH_NON_TAB) &&
 	    0 <= last_space_in_indent &&
 	    last_tab_in_indent < 0 &&
 	    8 <= (i - col0)) {
@@ -551,7 +552,7 @@ static void emit_line_with_ws(int nparents,
 	tail = len - 1;
 	if (line[tail] == '\n' && i < tail)
 		tail--;
-	if (whitespace_rule & WS_TRAILING_SPACE) {
+	if (ws_rule & WS_TRAILING_SPACE) {
 		while (i < tail) {
 			if (!isspace(line[tail]))
 				break;
@@ -578,7 +579,7 @@ static void emit_add_line(const char *reset, struct emit_callback *ecbdata, cons
 		emit_line(set, reset, line, len);
 	else
 		emit_line_with_ws(ecbdata->nparents, set, reset, ws,
-				line, len);
+				  line, len, ecbdata->ws_rule);
 }
 
 static void fn_out_consume(void *priv, char *line, unsigned long len)
@@ -994,6 +995,7 @@ struct checkdiff_t {
 	struct xdiff_emit_state xm;
 	const char *filename;
 	int lineno, color_diff;
+	unsigned ws_rule;
 };
 
 static void checkdiff_consume(void *priv, char *line, unsigned long len)
@@ -1029,7 +1031,8 @@ static void checkdiff_consume(void *priv, char *line, unsigned long len)
 			if (white_space_at_end)
 				printf("white space at end");
 			printf(":%s ", reset);
-			emit_line_with_ws(1, set, reset, ws, line, len);
+			emit_line_with_ws(1, set, reset, ws, line, len,
+					  data->ws_rule);
 		}
 
 		data->lineno++;
@@ -1330,6 +1333,7 @@ static void builtin_diff(const char *name_a,
 		ecbdata.label_path = lbl;
 		ecbdata.color_diff = o->color_diff;
 		ecbdata.found_changesp = &o->found_changes;
+		ecbdata.ws_rule = whitespace_rule(name_b ? name_b : name_a);
 		xpp.flags = XDF_NEED_MINIMAL | o->xdl_opts;
 		xecfg.ctxlen = o->context;
 		xecfg.flags = XDL_EMIT_FUNCNAMES;
@@ -1423,6 +1427,7 @@ static void builtin_checkdiff(const char *name_a, const char *name_b,
 	data.filename = name_b ? name_b : name_a;
 	data.lineno = 0;
 	data.color_diff = o->color_diff;
+	data.ws_rule = whitespace_rule(data.filename);
 
 	if (fill_mmfile(&mf1, one) < 0 || fill_mmfile(&mf2, two) < 0)
 		die("unable to read files to diff");