Subject: [PATCH v3 3/4] add-patch: respect diff.context configuration

From: "Leon Michalak via GitGitGadget" <[email-masked]>
Date: Sat, 28 Jun 2025 16:34:45 +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.
This patch fixes this inconsistency.

This is because the plumbing commands used by "git add -p" to generate
the diff do not read those config settings. Fix this by reading the
config before generating the patch and passing it along to the diff
command with the "-U" and "--inter-hunk-context" command-line options.

Signed-off-by: Leon Michalak <[email-masked]>
---
 add-interactive.c          | 17 +++++++++++++++++
 add-interactive.h          |  1 +
 add-patch.c                |  6 ++++++
 t/t3701-add-interactive.sh | 22 ++++++++++++++++++++++
 4 files changed, 46 insertions(+)

diff --git a/add-interactive.c b/add-interactive.c
index 97ff35b6f12a..e0aafb8dd02a 100644
--- a/add-interactive.c
+++ b/add-interactive.c
@@ -39,8 +39,12 @@ static void init_color(struct repository *r, struct add_i_state *s,
 void init_add_i_state(struct add_i_state *s, struct repository *r)
 {
 	const char *value;
+	int context;
+	int interhunkcontext;
 
 	s->r = r;
+	s->context = -1;
+	s->interhunkcontext = -1;
 
 	if (repo_config_get_value(r, "color.interactive", &value))
 		s->use_color = -1;
@@ -78,6 +82,19 @@ 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", &context)) {
+		if (context < 0)
+			die(_("%s cannot be negative"), "diff.context");
+		else
+			s->context = context;
+	}
+	if (!repo_config_get_int(r, "diff.interHunkContext", &interhunkcontext)) {
+		if (interhunkcontext < 0)
+			die(_("%s cannot be negative"), "diff.interHunkContext");
+		else
+			s->interhunkcontext = 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..b43ca1600738 100644
--- a/add-patch.c
+++ b/add-patch.c
@@ -415,6 +415,8 @@ 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;
+	int diff_context = s->s.context;
+	int diff_interhunkcontext = s->s.interhunkcontext;
 	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';
@@ -424,6 +426,10 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 	int res;
 
 	strvec_pushv(&args, s->mode->diff_cmd);
+	if (diff_context != -1)
+		strvec_pushf(&args, "--unified=%i", diff_context);
+	if (diff_interhunkcontext != -1)
+		strvec_pushf(&args, "--inter-hunk-context=%i", diff_interhunkcontext);
 	if (diff_algorithm)
 		strvec_pushf(&args, "--diff-algorithm=%s", diff_algorithm);
 	if (s->revision) {
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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