[PATCH 3/6] grep: print context hunk marks between files

["René Scharfe" <rene.scharfe@lsrfire.ath.cx>]

Print a hunk mark before matches from a new file are shown, in addition
to the current behaviour of printing them if lines have been skipped.

The result is easier to read, as (presumably unrelated) matches from
different files are separated by a hunk mark.  GNU grep does the same.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
---
 builtin-grep.c  |   11 +++++++++++
 grep.c          |    7 ++++++-
 grep.h          |    1 +
 t/t7002-grep.sh |   22 ++++++++++++++++++++++
 4 files changed, 40 insertions(+), 1 deletions(-)

diff --git a/builtin-grep.c b/builtin-grep.c
index 73fc922..48998af 100644
--- a/builtin-grep.c
+++ b/builtin-grep.c
@@ -278,6 +278,17 @@ static int flush_grep(struct grep_opt *opt,
 		argc -= 2;
 	}
 
+	if (opt->pre_context || opt->post_context) {
+		/*
+		 * grep handles hunk marks between files, but we need to
+		 * do that ourselves between multiple calls.
+		 */
+		if (opt->show_hunk_mark)
+			write_or_die(1, "--\n", 3);
+		else
+			opt->show_hunk_mark = 1;
+	}
+
 	status = exec_grep(argc, argv);
 
 	if (kept_0) {
diff --git a/grep.c b/grep.c
index 6ee80f7..4bca759 100644
--- a/grep.c
+++ b/grep.c
@@ -491,7 +491,12 @@ static void show_line(struct grep_opt *opt, char *bol, char *eol,
 	int rest = eol - bol;
 
 	if (opt->pre_context || opt->post_context) {
-		if (opt->last_shown && lno > opt->last_shown + 1)
+		if (opt->last_shown == 0) {
+			if (opt->show_hunk_mark)
+				fputs("--\n", stdout);
+			else
+				opt->show_hunk_mark = 1;
+		} else if (lno > opt->last_shown + 1)
 			fputs("--\n", stdout);
 	}
 	opt->last_shown = lno;
diff --git a/grep.h b/grep.h
index 0883214..730ffd6 100644
--- a/grep.h
+++ b/grep.h
@@ -85,6 +85,7 @@ struct grep_opt {
 	unsigned pre_context;
 	unsigned post_context;
 	unsigned last_shown;
+	int show_hunk_mark;
 };
 
 extern void append_grep_pattern(struct grep_opt *opt, const char *pat, const char *origin, int no, enum grep_pat_token t);
diff --git a/t/t7002-grep.sh b/t/t7002-grep.sh
index 7868af8..155bfdb 100755
--- a/t/t7002-grep.sh
+++ b/t/t7002-grep.sh
@@ -155,6 +155,28 @@ test_expect_success 'grep -e A --and --not -e B' '
 	test_cmp expected actual
 '
 
+cat >expected <<EOF
+y:y yy
+--
+z:zzz
+EOF
+
+# Create 1024 file names that sort between "y" and "z" to make sure
+# the two files are handled by different calls to an external grep.
+# This depends on MAXARGS in builtin-grep.c being 1024 or less.
+c32="0 1 2 3 4 5 6 7 8 9 a b c d e f g h i j k l m n o p q r s t u v"
+test_expect_success 'grep -C1, hunk mark between files' '
+	for a in $c32; do for b in $c32; do : >y-$a$b; done; done &&
+	git add y-?? &&
+	git grep -C1 "^[yz]" >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'grep -C1 --no-ext-grep, hunk mark between files' '
+	git grep -C1 --no-ext-grep "^[yz]" >actual &&
+	test_cmp expected actual
+'
+
 test_expect_success 'log grep setup' '
 	echo a >>file &&
 	test_tick &&
-- 
1.6.3.3