Merge branch 'cn/bom-in-gitignore' into maint

Teach the codepaths that read .gitignore and .gitattributes files
that these files encoded in UTF-8 may have UTF-8 BOM marker at the
beginning; this makes it in line with what we do for configuration
files already.

* cn/bom-in-gitignore:
  attr: skip UTF8 BOM at the beginning of the input file
  config: use utf8_bom[] from utf.[ch] in git_parse_source()
  utf8-bom: introduce skip_utf8_bom() helper
  add_excludes_from_file: clarify the bom skipping logic
  dir: allow a BOM at the beginning of exclude files

attr.c

@@ -12,6 +12,7 @@
 #include "exec_cmd.h"
 #include "attr.h"
 #include "dir.h"
+#include "utf8.h"
 
 const char git_attr__true[] = "(builtin)true";
 const char git_attr__false[] = "\0(builtin)false";
@@ -379,8 +380,12 @@ static struct attr_stack *read_attr_from_file(const char *path, int macro_ok)
 		return NULL;
 	}
 	res = xcalloc(1, sizeof(*res));
-	while (fgets(buf, sizeof(buf), fp))
-		handle_attr_line(res, buf, path, ++lineno, macro_ok);
+	while (fgets(buf, sizeof(buf), fp)) {
+		char *bufp = buf;
+		if (!lineno)
+			skip_utf8_bom(&bufp, strlen(bufp));
+		handle_attr_line(res, bufp, path, ++lineno, macro_ok);
+	}
 	fclose(fp);
 	return res;
 }

config.c

@@ -12,6 +12,7 @@
 #include "quote.h"
 #include "hashmap.h"
 #include "string-list.h"
+#include "utf8.h"
 
 struct config_source {
 	struct config_source *prev;
@@ -417,8 +418,7 @@ static int git_parse_source(config_fn_t fn, void *data)
 	struct strbuf *var = &cf->var;
 
 	/* U+FEFF Byte Order Mark in UTF8 */
-	static const unsigned char *utf8_bom = (unsigned char *) "\xef\xbb\xbf";
-	const unsigned char *bomptr = utf8_bom;
+	const char *bomptr = utf8_bom;
 
 	for (;;) {
 		int c = get_next_char();
@@ -426,7 +426,7 @@ static int git_parse_source(config_fn_t fn, void *data)
 			/* We are at the file beginning; skip UTF8-encoded BOM
 			 * if present. Sane editors won't put this in on their
 			 * own, but e.g. Windows Notepad will do it happily. */
-			if ((unsigned char) c == *bomptr) {
+			if (c == (*bomptr & 0377)) {
 				bomptr++;
 				continue;
 			} else {

dir.c

@@ -12,6 +12,7 @@
 #include "refs.h"
 #include "wildmatch.h"
 #include "pathspec.h"
+#include "utf8.h"
 
 struct path_simplify {
 	int len;
@@ -617,7 +618,12 @@ int add_excludes_from_file_to_list(const char *fname,
 	}
 
 	el->filebuf = buf;
+
+	if (skip_utf8_bom(&buf, size))
+		size -= buf - el->filebuf;
+
 	entry = buf;
+
 	for (i = 0; i < size; i++) {
 		if (buf[i] == '\n') {
 			if (entry != buf + i && entry[0] != '#') {

t/t7061-wtstatus-ignore.sh

@@ -20,6 +20,15 @@ test_expect_success 'status untracked directory with --ignored' '
 	test_cmp expected actual
 '
 
+test_expect_success 'same with gitignore starting with BOM' '
+	printf "\357\273\277ignored\n" >.gitignore &&
+	mkdir -p untracked &&
+	: >untracked/ignored &&
+	: >untracked/uncommitted &&
+	git status --porcelain --ignored >actual &&
+	test_cmp expected actual
+'
+
 cat >expected <<\EOF
 ?? .gitignore
 ?? actual

utf8.c

@@ -633,3 +633,14 @@ int is_hfs_dotgit(const char *path)
 
 	return 1;
 }
+
+const char utf8_bom[] = "\357\273\277";
+
+int skip_utf8_bom(char **text, size_t len)
+{
+	if (len < strlen(utf8_bom) ||
+	    memcmp(*text, utf8_bom, strlen(utf8_bom)))
+		return 0;
+	*text += strlen(utf8_bom);
+	return 1;
+}

utf8.h

@@ -13,6 +13,9 @@ int same_encoding(const char *, const char *);
 __attribute__((format (printf, 2, 3)))
 int utf8_fprintf(FILE *, const char *, ...);
 
+extern const char utf8_bom[];
+extern int skip_utf8_bom(char **, size_t);
+
 void strbuf_add_wrapped_text(struct strbuf *buf,
 		const char *text, int indent, int indent2, int width);
 void strbuf_add_wrapped_bytes(struct strbuf *buf, const char *data, int len,