[PATCH v5 5/7] builtin/grep.c: add '--column' option to 'git-grep(1)'

[Taylor Blau <me@ttaylorr.com>]

Teach 'git-grep(1)' a new option, '--column', to show the column
number of the first match on a non-context line. This makes it possible
to teach 'contrib/git-jump/git-jump' how to seek to the first matching
position of a grep match in your editor, and allows similar additional
scripting capabilities.

For example:

  $ git grep -n --column foo | head -n3
  .clang-format:51:14:# myFunction(foo, bar, baz);
  .clang-format:64:7:# int foo();
  .clang-format:75:8:# void foo()

Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 Documentation/git-grep.txt |  6 +++++-
 builtin/grep.c             |  4 ++++
 grep.c                     |  3 +++
 t/t7810-grep.sh            | 32 ++++++++++++++++++++++++++++++++
 4 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-grep.txt b/Documentation/git-grep.txt
index 18b494731f..75f1561112 100644
--- a/Documentation/git-grep.txt
+++ b/Documentation/git-grep.txt
@@ -13,7 +13,7 @@ SYNOPSIS
 	   [-v | --invert-match] [-h|-H] [--full-name]
 	   [-E | --extended-regexp] [-G | --basic-regexp]
 	   [-P | --perl-regexp]
-	   [-F | --fixed-strings] [-n | --line-number]
+	   [-F | --fixed-strings] [-n | --line-number] [--column]
 	   [-l | --files-with-matches] [-L | --files-without-match]
 	   [(-O | --open-files-in-pager) [<pager>]]
 	   [-z | --null]
@@ -169,6 +169,10 @@ providing this option will cause it to die.
 --line-number::
 	Prefix the line number to matching lines.
 
+--column::
+	Prefix the 1-indexed byte-offset of the first match on non-context lines. This
+	option is incompatible with '--invert-match', and extended expressions.
+
 -l::
 --files-with-matches::
 --name-only::
diff --git a/builtin/grep.c b/builtin/grep.c
index 5f32d2ce84..f9f516dfc4 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -829,6 +829,7 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 			    GREP_PATTERN_TYPE_PCRE),
 		OPT_GROUP(""),
 		OPT_BOOL('n', "line-number", &opt.linenum, N_("show line numbers")),
+		OPT_BOOL(0, "column", &opt.columnnum, N_("show column number of first match")),
 		OPT_NEGBIT('h', NULL, &opt.pathname, N_("don't show filenames"), 1),
 		OPT_BIT('H', NULL, &opt.pathname, N_("show filenames"), 1),
 		OPT_NEGBIT(0, "full-name", &opt.relative,
@@ -1111,6 +1112,9 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 		hit = grep_objects(&opt, &pathspec, the_repository, &list);
 	}
 
+	if (opt.columnnum && opt.invert)
+		die(_("--column and --invert-match cannot be combined"));
+
 	if (num_threads)
 		hit |= wait_all();
 	if (hit && show_in_pager)
diff --git a/grep.c b/grep.c
index f3fe416791..f4228c23ac 100644
--- a/grep.c
+++ b/grep.c
@@ -995,6 +995,9 @@ static void compile_grep_patterns_real(struct grep_opt *opt)
 	else if (!opt->extended && !opt->debug)
 		return;
 
+	if (opt->columnnum && opt->extended)
+		die(_("--column and extended expressions cannot be combined"));
+
 	p = opt->pattern_list;
 	if (p)
 		opt->pattern_expression = compile_pattern_expr(&p);
diff --git a/t/t7810-grep.sh b/t/t7810-grep.sh
index 1797f632a3..aa56b21ed9 100755
--- a/t/t7810-grep.sh
+++ b/t/t7810-grep.sh
@@ -99,6 +99,28 @@ do
 		test_cmp expected actual
 	'
 
+	test_expect_success "grep -w $L (with --column)" '
+		{
+			echo ${HC}file:5:foo mmap bar
+			echo ${HC}file:14:foo_mmap bar mmap
+			echo ${HC}file:5:foo mmap bar_mmap
+			echo ${HC}file:14:foo_mmap bar mmap baz
+		} >expected &&
+		git grep --column -w -e mmap $H >actual &&
+		test_cmp expected actual
+	'
+
+	test_expect_success "grep -w $L (with --line-number, --column)" '
+		{
+			echo ${HC}file:1:5:foo mmap bar
+			echo ${HC}file:3:14:foo_mmap bar mmap
+			echo ${HC}file:4:5:foo mmap bar_mmap
+			echo ${HC}file:5:14:foo_mmap bar mmap baz
+		} >expected &&
+		git grep -n --column -w -e mmap $H >actual &&
+		test_cmp expected actual
+	'
+
 	test_expect_success "grep -w $L" '
 		{
 			echo ${HC}file:1:foo mmap bar
@@ -1590,4 +1612,14 @@ test_expect_success 'grep does not report i-t-a and assume unchanged with -L' '
 	test_cmp expected actual
 '
 
+test_expect_success 'grep does not allow --column, --invert-match' '
+	test_must_fail git grep --column --invert-match pat 2>err &&
+	test_i18ngrep "\-\-column and \-\-invert-match cannot be combined" err
+'
+
+test_expect_success 'grep does not allow --column, extended' '
+	test_must_fail git grep --column --not -e pat 2>err &&
+	test_i18ngrep "\-\-column and extended expressions cannot be combined" err
+'
+
 test_done
-- 
2.17.0