Subject: [PATCH v4 3/4] add-patch: respect diff.context configuration

From: "Leon Michalak via GitGitGadget" <[email-masked]>
Date: Sat, 19 Jul 2025 12:28:32 +0000

From: Leon Michalak <[email-masked]>

Various builtins that use add-patch infrastructure do not respect
the user's diff.context and diff.interHunkContext file configurations.

The user may be used to seeing their diffs with customized context size,
but not in the patches "git add -p" shows them to pick from.

Teach add-patch infrastructure to read these configuration variables and
pass their values when spawning the underlying plumbing commands as
their command line option.

Signed-off-by: Leon Michalak <[email-masked]>
---
 add-interactive.c          |  9 +++++++++
 add-interactive.h          |  1 +
 add-patch.c                |  9 ++++++---
 t/t3701-add-interactive.sh | 22 ++++++++++++++++++++++
 4 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/add-interactive.c b/add-interactive.c
index 97ff35b6f12a..eb3d0d3ada84 100644
--- a/add-interactive.c
+++ b/add-interactive.c
@@ -41,6 +41,8 @@ void init_add_i_state(struct add_i_state *s, struct repository *r)
 	const char *value;
 
 	s->r = r;
+	s->context = -1;
+	s->interhunkcontext = -1;
 
 	if (repo_config_get_value(r, "color.interactive", &value))
 		s->use_color = -1;
@@ -78,6 +80,13 @@ void init_add_i_state(struct add_i_state *s, struct repository *r)
 	repo_config_get_string(r, "diff.algorithm",
 			       &s->interactive_diff_algorithm);
 
+	if (!repo_config_get_int(r, "diff.context", &s->context))
+		if (s->context < 0)
+			die(_("%s cannot be negative"), "diff.context");
+	if (!repo_config_get_int(r, "diff.interHunkContext", &s->interhunkcontext))
+		if (s->interhunkcontext < 0)
+			die(_("%s cannot be negative"), "diff.interHunkContext");
+
 	repo_config_get_bool(r, "interactive.singlekey", &s->use_single_key);
 	if (s->use_single_key)
 		setbuf(stdin, NULL);
diff --git a/add-interactive.h b/add-interactive.h
index 693f125e8e4b..c63f35b14be8 100644
--- a/add-interactive.h
+++ b/add-interactive.h
@@ -18,6 +18,7 @@ struct add_i_state {
 
 	int use_single_key;
 	char *interactive_diff_filter, *interactive_diff_algorithm;
+	int context, interhunkcontext;
 };
 
 void init_add_i_state(struct add_i_state *s, struct repository *r);
diff --git a/add-patch.c b/add-patch.c
index 95c67d8c80c4..b0125b51ba45 100644
--- a/add-patch.c
+++ b/add-patch.c
@@ -414,7 +414,6 @@ static int normalize_marker(const char *p)
 static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 {
 	struct strvec args = STRVEC_INIT;
-	const char *diff_algorithm = s->s.interactive_diff_algorithm;
 	struct strbuf *plain = &s->plain, *colored = NULL;
 	struct child_process cp = CHILD_PROCESS_INIT;
 	char *p, *pend, *colored_p = NULL, *colored_pend = NULL, marker = '\0';
@@ -424,8 +423,12 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 	int res;
 
 	strvec_pushv(&args, s->mode->diff_cmd);
-	if (diff_algorithm)
-		strvec_pushf(&args, "--diff-algorithm=%s", diff_algorithm);
+	if (s->s.context != -1)
+		strvec_pushf(&args, "--unified=%i", s->s.context);
+	if (s->s.interhunkcontext != -1)
+		strvec_pushf(&args, "--inter-hunk-context=%i", s->s.interhunkcontext);
+	if (s->s.interactive_diff_algorithm)
+		strvec_pushf(&args, "--diff-algorithm=%s", s->s.interactive_diff_algorithm);
 	if (s->revision) {
 		struct object_id oid;
 		strvec_push(&args,
diff --git a/t/t3701-add-interactive.sh b/t/t3701-add-interactive.sh
index b088ee141ff4..18dc329ea1f6 100755
--- a/t/t3701-add-interactive.sh
+++ b/t/t3701-add-interactive.sh
@@ -1230,4 +1230,26 @@ test_expect_success 'hunk splitting works with diff.suppressBlankEmpty' '
 	test_cmp expect actual
 '
 
+test_expect_success 'add -p respects diff.context' '
+	test_write_lines a b c d e f g h i j k l m >file &&
+	git add file &&
+	test_write_lines a b c d e f G h i j k l m >file &&
+	echo y | git -c diff.context=5 add -p >actual &&
+	test_grep "@@ -2,11 +2,11 @@" actual
+'
+
+test_expect_success 'add -p respects diff.interHunkContext' '
+	test_write_lines a b c d e f g h i j k l m n o p q r s >file &&
+	git add file &&
+	test_write_lines a b c d E f g i i j k l m N o p q r s >file &&
+	echo y | git -c diff.interhunkcontext=2 add -p >actual &&
+	test_grep "@@ -2,16 +2,16 @@" actual
+'
+
+test_expect_success 'add -p rejects negative diff.context' '
+	test_config diff.context -1 &&
+	test_must_fail git add -p 2>output &&
+	test_grep "diff.context cannot be negative" output
+'
+
 test_done
-- 
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