[PATCH] diff: diff.context configuration gives default to -U

@@ -56,6 +56,10 @@ diff.statGraphWidth::
 	Limit the width of the graph part in --stat output. If set, applies
 	to all commands generating --stat output except format-patch.
 
+diff.context::
+	Generate diffs with <n> lines of context instead of the default of
+	3. This value is overridden by the -U option.
+
 diff.external::
 	If this config variable is set, diff generation is not
 	performed using the internal diff machinery, but using the

@@ -26,6 +26,7 @@ static int diff_detect_rename_default;
 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 const char *diff_word_regex_cfg;
 static const char *external_diff_cmd_cfg;
 int diff_auto_refresh_index = 1;

@@ -141,6 +142,12 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
 		diff_use_color_default = git_config_colorbool(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "diff.context")) {
+		diff_context_default = git_config_int(var, value);
+		if (diff_context_default < 0)
+			return -1;
+		return 0;
+	}
 	if (!strcmp(var, "diff.renames")) {
 		diff_detect_rename_default = git_config_rename(var, value);
 		return 0;

@@ -3170,7 +3177,7 @@ void diff_setup(struct diff_options *options)
 	options->break_opt = -1;
 	options->rename_limit = -1;
 	options->dirstat_permille = diff_dirstat_permille_default;
-	options->context = 3;
+	options->context = diff_context_default;
 	DIFF_OPT_SET(options, RENAME_EMPTY);
 
 	options->change = diff_change;

@@ -0,0 +1,127 @@
+#!/bin/sh
+#
+# Copyright (c) 2012 Mozilla Foundation
+#
+
+test_description='diff.context configuration'
+
+. ./test-lib.sh
+
+cat << EOF > x
+firstline
+b
+c
+d
+e
+f
+preline
+postline
+i
+j
+k
+l
+m
+n
+EOF
+test_expect_success 'initial add' '
+	git update-index --add x &&
+	git commit -m initial
+'
+
+cat << EOF > x
+firstline
+b
+c
+d
+e
+f
+preline
+1
+postline
+i
+j
+k
+l
+m
+n
+EOF
+
+test_expect_success 'next commit' '
+	git update-index --add x &&
+	git commit -m next
+'
+cat << EOF > x
+firstline
+b
+c
+d
+e
+f
+preline
+2
+postline
+i
+j
+k
+l
+m
+n
+EOF
+
+
+
+
+test_expect_success 'diff.context affects log' '
+	git log -1 -p | grep -q -v firstline
+	git config diff.context 8 &&
+	git log -1 -p | grep -q firstline
+'
+test_expect_success 'different -U value' '
+	git config diff.context 8 &&
+	git log -U4 -1 | grep -q -v firstline
+'
+
+test_expect_success 'diff.context affects diff' '
+	git config diff.context 8 &&
+	git diff | grep -q firstline
+'
+
+test_expect_success 'plumbing not affected' '
+	git config diff.context 8 &&
+	git diff-files -p | grep -q -v firstline
+'
+
+cat > .git/config << EOF
+[diff]
+	context = no
+EOF
+test_expect_success 'config parsing' '
+	git diff 2>&1 | grep -q "bad config value"
+'
+
+cat > .git/config << EOF
+[diff]
+	context = 0
+EOF
+test_expect_success 'config parsing' '
+	git diff | grep -v preline
+'
+
+cat > .git/config << EOF
+[diff]
+	context = -1
+EOF
+test_expect_success 'config parsing' '
+	git diff 2>&1 | grep -q "bad config file"
+'
+
+cat > .git/config << EOF
+[diff]
+	context = 8
+EOF
+test_expect_success 'config parsing' '
+	git diff 2>&1 | grep "postline"
+'
+
+
+test_done