grep: add option to show whole function as context

Add a new option, -W, to show the whole surrounding function of a match.

It uses the same regular expressions as -p and diff to find the beginning
of sections.

Currently it will not display comments in front of a function, but those
that are following one.  Despite this shortcoming it is already useful,
e.g. to simply see a more complete applicable context or to extract whole
functions.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-grep.txt

@@ -172,6 +172,12 @@ OPTIONS
 	patch hunk headers (see 'Defining a custom hunk-header' in
 	linkgit:gitattributes[5]).
 
+-W::
+	Show the surrounding text from the previous line containing a
+	function name up to the one before the next function name,
+	effectively showing the whole function in which the match was
+	found.
+
 -f <file>::
 	Read patterns from <file>, one per line.
 

builtin/grep.c

@@ -838,6 +838,8 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 			context_callback),
 		OPT_BOOLEAN('p', "show-function", &opt.funcname,
 			"show a line with the function name before matches"),
+		OPT_BOOLEAN('W', NULL, &opt.funcbody,
+			"show the surrounding function"),
 		OPT_GROUP(""),
 		OPT_CALLBACK('f', NULL, &opt, "file",
 			"read patterns from file", file_callback),
@@ -980,7 +982,8 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 		use_threads = 0;
 
 	if (use_threads) {
-		if (opt.pre_context || opt.post_context || opt.file_break)
+		if (opt.pre_context || opt.post_context || opt.file_break ||
+		    opt.funcbody)
 			skip_first_line = 1;
 		start_threads(&opt);
 	}

grep.c

@@ -724,7 +724,7 @@ static void show_line(struct grep_opt *opt, char *bol, char *eol,
 	if (opt->file_break && opt->last_shown == 0) {
 		if (opt->show_hunk_mark)
 			opt->output(opt, "\n", 1);
-	} else if (opt->pre_context || opt->post_context) {
+	} else if (opt->pre_context || opt->post_context || opt->funcbody) {
 		if (opt->last_shown == 0) {
 			if (opt->show_hunk_mark) {
 				output_color(opt, "--", 2, opt->color_sep);
@@ -819,10 +819,13 @@ static void show_funcname_line(struct grep_opt *opt, const char *name,
 }
 
 static void show_pre_context(struct grep_opt *opt, const char *name, char *buf,
-			     char *bol, unsigned lno)
+			     char *bol, char *end, unsigned lno)
 {
 	unsigned cur = lno, from = 1, funcname_lno = 0;
-	int funcname_needed = opt->funcname;
+	int funcname_needed = !!opt->funcname;
+
+	if (opt->funcbody && !match_funcname(opt, bol, end))
+		funcname_needed = 2;
 
 	if (opt->pre_context < lno)
 		from = lno - opt->pre_context;
@@ -830,7 +833,8 @@ static void show_pre_context(struct grep_opt *opt, const char *name, char *buf,
 		from = opt->last_shown + 1;
 
 	/* Rewind. */
-	while (bol > buf && cur > from) {
+	while (bol > buf &&
+	       cur > (funcname_needed == 2 ? opt->last_shown + 1 : from)) {
 		char *eol = --bol;
 
 		while (bol > buf && bol[-1] != '\n')
@@ -942,13 +946,15 @@ static int grep_buffer_1(struct grep_opt *opt, const char *name,
 	int binary_match_only = 0;
 	unsigned count = 0;
 	int try_lookahead = 0;
+	int show_function = 0;
 	enum grep_context ctx = GREP_CONTEXT_HEAD;
 	xdemitconf_t xecfg;
 
 	if (!opt->output)
 		opt->output = std_output;
 
-	if (opt->pre_context || opt->post_context || opt->file_break) {
+	if (opt->pre_context || opt->post_context || opt->file_break ||
+	    opt->funcbody) {
 		/* Show hunk marks, except for the first file. */
 		if (opt->last_shown)
 			opt->show_hunk_mark = 1;
@@ -1004,7 +1010,8 @@ static int grep_buffer_1(struct grep_opt *opt, const char *name,
 		 */
 		if (try_lookahead
 		    && !(last_hit
-			 && lno <= last_hit + opt->post_context)
+			 && (show_function ||
+			     lno <= last_hit + opt->post_context))
 		    && look_ahead(opt, &left, &lno, &bol))
 			break;
 		eol = end_of_line(bol, &left);
@@ -1051,15 +1058,20 @@ static int grep_buffer_1(struct grep_opt *opt, const char *name,
 			/* Hit at this line.  If we haven't shown the
 			 * pre-context lines, we would need to show them.
 			 */
-			if (opt->pre_context)
-				show_pre_context(opt, name, buf, bol, lno);
+			if (opt->pre_context || opt->funcbody)
+				show_pre_context(opt, name, buf, bol, eol, lno);
 			else if (opt->funcname)
 				show_funcname_line(opt, name, buf, bol, lno);
 			show_line(opt, bol, eol, name, lno, ':');
 			last_hit = lno;
+			if (opt->funcbody)
+				show_function = 1;
+			goto next_line;
 		}
-		else if (last_hit &&
-			 lno <= last_hit + opt->post_context) {
+		if (show_function && match_funcname(opt, bol, eol))
+			show_function = 0;
+		if (show_function ||
+		    (last_hit && lno <= last_hit + opt->post_context)) {
 			/* If the last hit is within the post context,
 			 * we need to show this line.
 			 */

grep.h

@@ -98,6 +98,7 @@ struct grep_opt {
 	int color;
 	int max_depth;
 	int funcname;
+	int funcbody;
 	char color_context[COLOR_MAXLEN];
 	char color_filename[COLOR_MAXLEN];
 	char color_function[COLOR_MAXLEN];

t/t7810-grep.sh

@@ -509,6 +509,20 @@ test_expect_success 'grep -p -B5' '
 	test_cmp expected actual
 '
 
+cat >expected <<EOF
+hello.c=int main(int argc, const char **argv)
+hello.c-{
+hello.c-	printf("Hello world.\n");
+hello.c:	return 0;
+hello.c-	/* char ?? */
+hello.c-}
+EOF
+
+test_expect_success 'grep -W' '
+	git grep -W return >actual &&
+	test_cmp expected actual
+'
+
 test_expect_success 'grep from a subdirectory to search wider area (1)' '
 	mkdir -p s &&
 	(