Subject: [PATCH v2 1/4] diff: reject negative values for --inter-hunk-context

From: "Michael Montalbo via GitGitGadget" <[email-masked]>
Date: Tue, 12 May 2026 18:10:20 +0000

From: Michael Montalbo <[email-masked]>

Negative values for --inter-hunk-context produce structurally invalid
diff output with overlapping hunks:

    $ git log -1 -p -U3 --inter-hunk-context=-100 791aeddfa2 \
        -- git-compat-util.h | grep '^@@'
    @@ -110,6 +110,9 @@
    @@ -115,6 +118,9 @@
    @@ -116,6 +122,7 @@

Hunk 1 covers lines 110-115, hunk 2 starts at 115 (overlap), hunk 3
starts at 116 (overlaps both). The resulting patch cannot be applied.

The config variable diff.interHunkContext already rejects negative
values, but the command line option does not.

Change the type of diff_options.interhunkcontext and its static
default from int to unsigned int, and switch the option parser from
OPT_INTEGER_F to OPT_UNSIGNED. This rejects negative values at parse
time via git_parse_unsigned() and enforces the correct type at compile
time via BARF_UNLESS_UNSIGNED.

Signed-off-by: Michael Montalbo <[email-masked]>
---
 diff.c                             | 13 ++++++-------
 diff.h                             |  2 +-
 t/t4032-diff-inter-hunk-context.sh |  6 ++++++
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/diff.c b/diff.c
index 397e38b41c..5df28e49c5 100644
--- a/diff.c
+++ b/diff.c
@@ -61,7 +61,7 @@ static enum git_colorbool diff_use_color_default = GIT_COLOR_UNKNOWN;
 static int diff_color_moved_default;
 static int diff_color_moved_ws_default;
 static int diff_context_default = 3;
-static int diff_interhunk_context_default;
+static unsigned int diff_interhunk_context_default;
 static char *diff_word_regex_cfg;
 static struct external_diff external_diff_cfg;
 static char *diff_order_file_cfg;
@@ -388,10 +388,10 @@ int git_diff_ui_config(const char *var, const char *value,
 		return 0;
 	}
 	if (!strcmp(var, "diff.interhunkcontext")) {
-		diff_interhunk_context_default = git_config_int(var, value,
-								ctx->kvi);
-		if (diff_interhunk_context_default < 0)
+		int val = git_config_int(var, value, ctx->kvi);
+		if (val < 0)
 			return -1;
+		diff_interhunk_context_default = val;
 		return 0;
 	}
 	if (!strcmp(var, "diff.renames")) {
@@ -6111,9 +6111,8 @@ struct option *add_diff_options(const struct option *opts,
 		OPT_CALLBACK_F(0, "default-prefix", options, NULL,
 			       N_("use default prefixes a/ and b/"),
 			       PARSE_OPT_NONEG | PARSE_OPT_NOARG, diff_opt_default_prefix),
-		OPT_INTEGER_F(0, "inter-hunk-context", &options->interhunkcontext,
-			      N_("show context between diff hunks up to the specified number of lines"),
-			      PARSE_OPT_NONEG),
+		OPT_UNSIGNED(0, "inter-hunk-context", &options->interhunkcontext,
+			     N_("show context between diff hunks up to the specified number of lines")),
 		OPT_CALLBACK_F(0, "output-indicator-new",
 			       &options->output_indicators[OUTPUT_INDICATOR_NEW],
 			       N_("<char>"),
diff --git a/diff.h b/diff.h
index 7eb84aadf4..033d633db4 100644
--- a/diff.h
+++ b/diff.h
@@ -296,7 +296,7 @@ struct diff_options {
 	/* Number of context lines to generate in patch output. */
 	int context;
 
-	int interhunkcontext;
+	unsigned int interhunkcontext;
 
 	/* Affects the way detection logic for complete rewrites, renames and
 	 * copies.
diff --git a/t/t4032-diff-inter-hunk-context.sh b/t/t4032-diff-inter-hunk-context.sh
index bada0cbd32..bec1676f8d 100755
--- a/t/t4032-diff-inter-hunk-context.sh
+++ b/t/t4032-diff-inter-hunk-context.sh
@@ -114,4 +114,10 @@ test_expect_success 'diff.interHunkContext invalid' '
 	test_must_fail git diff
 '
 
+test_expect_success '--inter-hunk-context rejects negative value' '
+	test_unconfig diff.interHunkContext &&
+	test_must_fail git diff --inter-hunk-context=-1 2>err &&
+	test_grep "expects a non-negative integer" err
+'
+
 test_done
-- 
gitgitgadget