Merge branch 'vn/diff-ihc-config'

"git diff" learned diff.interHunkContext configuration variable
that gives the default value for its --inter-hunk-context option.

* vn/diff-ihc-config:
  diff: add interhunk context config option

Documentation/diff-config.txt

@@ -60,6 +60,12 @@ diff.context::
 	Generate diffs with <n> lines of context instead of the default
 	of 3. This value is overridden by the -U option.
 
+diff.interHunkContext::
+	Show the context between diff hunks, up to the specified number
+	of lines, thereby fusing the hunks that are close to each other.
+	This value serves as the default for the `--inter-hunk-context`
+	command line option.
+
 diff.external::
 	If this config variable is set, diff generation is not
 	performed using the internal diff machinery, but using the

Documentation/diff-options.txt

@@ -511,6 +511,8 @@ endif::git-format-patch[]
 --inter-hunk-context=<lines>::
 	Show the context between diff hunks, up to the specified number
 	of lines, thereby fusing hunks that are close to each other.
+	Defaults to `diff.interHunkContext` or 0 if the config option
+	is unset.
 
 -W::
 --function-context::

diff.c

@@ -32,6 +32,7 @@ static int diff_rename_limit_default = 400;
 static int diff_suppress_blank_empty;
 static int diff_use_color_default = -1;
 static int diff_context_default = 3;
+static int diff_interhunk_context_default;
 static const char *diff_word_regex_cfg;
 static const char *external_diff_cmd_cfg;
 static const char *diff_order_file_cfg;
@@ -239,6 +240,12 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
 			return -1;
 		return 0;
 	}
+	if (!strcmp(var, "diff.interhunkcontext")) {
+		diff_interhunk_context_default = git_config_int(var, value);
+		if (diff_interhunk_context_default < 0)
+			return -1;
+		return 0;
+	}
 	if (!strcmp(var, "diff.renames")) {
 		diff_detect_rename_default = git_config_rename(var, value);
 		return 0;
@@ -3362,6 +3369,7 @@ void diff_setup(struct diff_options *options)
 	options->rename_limit = -1;
 	options->dirstat_permille = diff_dirstat_permille_default;
 	options->context = diff_context_default;
+	options->interhunkcontext = diff_interhunk_context_default;
 	options->ws_error_highlight = ws_error_highlight_default;
 	DIFF_OPT_SET(options, RENAME_EMPTY);
 

t/t4032-diff-inter-hunk-context.sh

@@ -16,11 +16,15 @@ f() {
 }
 
 t() {
+	use_config=
+	git config --unset diff.interHunkContext
+
 	case $# in
 	4) hunks=$4; cmd="diff -U$3";;
 	5) hunks=$5; cmd="diff -U$3 --inter-hunk-context=$4";;
+	6) hunks=$5; cmd="diff -U$3"; git config diff.interHunkContext $4; use_config="(diff.interHunkContext=$4) ";;
 	esac
-	label="$cmd, $1 common $2"
+	label="$use_config$cmd, $1 common $2"
 	file=f$1
 	expected=expected.$file.$3.$hunks
 
@@ -89,4 +93,25 @@ t 9 lines	3		2
 t 9 lines	3	2	2
 t 9 lines	3	3	1
 
+#					use diff.interHunkContext?
+t 1 line	0	0	2	config
+t 1 line	0	1	1	config
+t 1 line	0	2	1	config
+t 9 lines	3	3	1	config
+t 2 lines	0	0	2	config
+t 2 lines	0	1	2	config
+t 2 lines	0	2	1	config
+t 3 lines	1	0	2	config
+t 3 lines	1	1	1	config
+t 3 lines	1	2	1	config
+t 9 lines	3	2	2	config
+t 9 lines	3	3	1	config
+
+test_expect_success 'diff.interHunkContext invalid' '
+	git config diff.interHunkContext asdf &&
+	test_must_fail git diff &&
+	git config diff.interHunkContext -1 &&
+	test_must_fail git diff
+'
+
 test_done