grep: Add the option '--open-files-in-pager'

This adds an option to open the matching files in the pager, and if the
pager happens to be "less" (or "vi") and there is only one grep pattern,
it also jumps to the first match right away.

The short option was chose as '-O' to avoid clashes with GNU grep's
options (as suggested by Junio).

So, 'git grep -O abc' is a short form for 'less +/abc $(grep -l abc)'
except that it works also with spaces in file names, and it does not
start the pager if there was no matching file.

[jn: rebased and added tests; with error handling fix from Junio
squashed in]

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

4 files changed, 173 insertions, 12 deletions

diff --git a/t/lib-pager.sh b/t/lib-pager.sh
new file mode 100644
index 000000000..f8c602587
--- /dev/null
+++ b/t/lib-pager.sh
@@ -0,0 +1,15 @@
+#!/bin/sh
+
+test_expect_success 'determine default pager' '
+	test_might_fail git config --unset core.pager &&
+	less=$(
+		unset PAGER GIT_PAGER;
+		git var GIT_PAGER
+	) &&
+	test -n "$less"
+'
+
+if expr "$less" : '^[a-z][a-z]*$' >/dev/null
+then
+	test_set_prereq SIMPLEPAGER
+fi
diff --git a/t/t7006-pager.sh b/t/t7006-pager.sh
index 3bc7a2a79..fc993fc8c 100755
--- a/t/t7006-pager.sh
+++ b/t/t7006-pager.sh
@@ -3,6 +3,7 @@
 test_description='Test automatic use of a pager.'
 
 . ./test-lib.sh
+. "$TEST_DIRECTORY"/lib-pager.sh
 
 cleanup_fail() {
 	echo >&2 cleanup failed
@@ -158,21 +159,12 @@ test_expect_success 'color when writing to a file intended for a pager' '
 	colorful colorful.log
 '
 
-test_expect_success 'determine default pager' '
-	unset PAGER GIT_PAGER &&
-	test_might_fail git config --unset core.pager ||
-	cleanup_fail &&
-
-	less=$(git var GIT_PAGER) &&
-	test -n "$less"
-'
-
-if expr "$less" : '^[a-z][a-z]*$' >/dev/null && test_have_prereq TTY
+if test_have_prereq SIMPLEPAGER && test_have_prereq TTY
 then
-	test_set_prereq SIMPLEPAGER
+	test_set_prereq SIMPLEPAGERTTY
 fi
 
-test_expect_success SIMPLEPAGER 'default pager is used by default' '
+test_expect_success SIMPLEPAGERTTY 'default pager is used by default' '
 	unset PAGER GIT_PAGER &&
 	test_might_fail git config --unset core.pager &&
 	rm -f default_pager_used ||
diff --git a/t/t7002-grep.sh b/t/t7810-grep.sh
index e249c3ed4..e249c3ed4 100755
--- a/t/t7002-grep.sh
+++ b/t/t7810-grep.sh
diff --git a/t/t7811-grep-open.sh b/t/t7811-grep-open.sh
new file mode 100755
index 000000000..fcfc56ea6
--- /dev/null
+++ b/t/t7811-grep-open.sh
@@ -0,0 +1,154 @@
+#!/bin/sh
+
+test_description='git grep --open-files-in-pager
+'
+
+. ./test-lib.sh
+. "$TEST_DIRECTORY"/lib-pager.sh
+unset PAGER GIT_PAGER
+
+test_expect_success 'setup' '
+	test_commit initial grep.h "
+enum grep_pat_token {
+	GREP_PATTERN,
+	GREP_PATTERN_HEAD,
+	GREP_PATTERN_BODY,
+	GREP_AND,
+	GREP_OPEN_PAREN,
+	GREP_CLOSE_PAREN,
+	GREP_NOT,
+	GREP_OR,
+};" &&
+
+	test_commit add-user revision.c "
+	}
+	if (seen_dashdash)
+		read_pathspec_from_stdin(revs, &sb, prune);
+	strbuf_release(&sb);
+}
+
+static void add_grep(struct rev_info *revs, const char *ptn, enum grep_pat_token what)
+{
+	append_grep_pattern(&revs->grep_filter, ptn, \"command line\", 0, what);
+" &&
+
+	mkdir subdir &&
+	test_commit subdir subdir/grep.c "enum grep_pat_token" &&
+
+	test_commit uninteresting unrelated "hello, world" &&
+
+	echo GREP_PATTERN >untracked
+'
+
+test_expect_success SIMPLEPAGER 'git grep -O' '
+	cat >$less <<-\EOF &&
+	#!/bin/sh
+	printf "%s\n" "$@" >pager-args
+	EOF
+	chmod +x $less &&
+	cat >expect.less <<-\EOF &&
+	+/*GREP_PATTERN
+	grep.h
+	EOF
+	echo grep.h >expect.notless &&
+	>empty &&
+
+	PATH=.:$PATH git grep -O GREP_PATTERN >out &&
+	{
+		test_cmp expect.less pager-args ||
+		test_cmp expect.notless pager-args
+	} &&
+	test_cmp empty out
+'
+
+test_expect_success 'git grep -O --cached' '
+	test_must_fail git grep --cached -O GREP_PATTERN >out 2>msg &&
+	grep open-files-in-pager msg
+'
+
+test_expect_success 'git grep -O --no-index' '
+	rm -f expect.less pager-args out &&
+	cat >expect <<-\EOF &&
+	grep.h
+	untracked
+	EOF
+	>empty &&
+
+	(
+		GIT_PAGER='\''printf "%s\n" >pager-args'\'' &&
+		export GIT_PAGER &&
+		git grep --no-index -O GREP_PATTERN >out
+	) &&
+	test_cmp expect pager-args &&
+	test_cmp empty out
+'
+
+test_expect_success 'setup: fake "less"' '
+	cat >less <<-\EOF
+	#!/bin/sh
+	printf "%s\n" "$@" >actual
+	EOF
+'
+
+test_expect_success 'git grep -O jumps to line in less' '
+	cat >expect <<-\EOF &&
+	+/*GREP_PATTERN
+	grep.h
+	EOF
+	>empty &&
+
+	GIT_PAGER=./less git grep -O GREP_PATTERN >out &&
+	test_cmp expect actual &&
+	test_cmp empty out
+'
+
+test_expect_success 'modified file' '
+	rm -f actual &&
+	cat >less <<-\EOF &&
+	#!/bin/sh
+	printf "%s\n" "$@" >actual
+	EOF
+	chmod +x $less &&
+	cat >expect <<-\EOF &&
+	+/*enum grep_pat_token
+	grep.h
+	revision.c
+	subdir/grep.c
+	unrelated
+	EOF
+	>empty &&
+
+	echo "enum grep_pat_token" >unrelated &&
+	test_when_finished "git checkout HEAD unrelated" &&
+	GIT_PAGER=./less git grep -F -O "enum grep_pat_token" >out &&
+	test_cmp expect actual &&
+	test_cmp empty out
+'
+
+test_expect_success 'run from subdir' '
+	rm -f actual &&
+	echo grep.c >expect &&
+	>empty &&
+
+	(
+		cd subdir &&
+		export GIT_PAGER &&
+		GIT_PAGER='\''printf "%s\n" >../args'\'' &&
+		git grep -O "enum grep_pat_token" >../out &&
+		GIT_PAGER="pwd >../dir; :" &&
+		git grep -O "enum grep_pat_token" >../out2
+	) &&
+	case $(cat dir) in
+	*subdir)
+		: good
+		;;
+	*)
+		false
+		;;
+	esac &&
+	test_cmp expect args &&
+	test_cmp empty out &&
+	test_cmp empty out2
+'
+
+test_done