[PATCH 2/2] diff: add 'diff.wordDiff' config option

[Karthik Nayak <karthik.188@xxxxxxxxx>]

The git-diff(1) command supports the `--word-diff` which allows the
users to specify how to delimit word diffs. Provide this option also as
a config param 'diff.wordDiff'.

Signed-off-by: Karthik Nayak <karthik.188@xxxxxxxxx>
---
 Documentation/config/diff.txt |  4 +++
 diff.c                        | 50 +++++++++++++++++++++++++++--------
 t/t4034-diff-words.sh         | 11 ++++++--
 3 files changed, 52 insertions(+), 13 deletions(-)

diff --git a/Documentation/config/diff.txt b/Documentation/config/diff.txt
index bd5ae0c337..00459beee2 100644
--- a/Documentation/config/diff.txt
+++ b/Documentation/config/diff.txt
@@ -225,3 +225,7 @@ diff.colorMovedWS::
 	When moved lines are colored using e.g. the `diff.colorMoved` setting,
 	this option controls the `<mode>` how spaces are treated
 	for details of valid modes see '--color-moved-ws' in linkgit:git-diff[1].
+
+diff.wordDiff::
+	Show a word diff, using the `<mode>` to delimit changed words.
+	For details of valid modes see '--word-diff' in linkgit:git-diff[1].
diff --git a/diff.c b/diff.c
index e50def4538..050d83ef85 100644
--- a/diff.c
+++ b/diff.c
@@ -69,6 +69,7 @@ static int diff_dirstat_permille_default = 30;
 static struct diff_options default_diff_options;
 static long diff_algorithm;
 static unsigned ws_error_highlight_default = WSEH_NEW;
+static int diff_word_diff_default;
 
 static char diff_colors[][COLOR_MAXLEN] = {
 	GIT_COLOR_RESET,
@@ -209,6 +210,23 @@ int git_config_rename(const char *var, const char *value)
 	return git_config_bool(var,value) ? DIFF_DETECT_RENAME : 0;
 }
 
+static int parse_word_diff_value(const char *value)
+{
+	if (!value)
+		return -1;
+	else if (!strcmp(value, "plain"))
+		return DIFF_WORDS_PLAIN;
+	else if (!strcmp(value, "color")) {
+		return DIFF_WORDS_COLOR;
+	}
+	else if (!strcmp(value, "porcelain"))
+		return DIFF_WORDS_PORCELAIN;
+	else if (!strcmp(value, "none"))
+		return DIFF_WORDS_NONE;
+
+	return -1;
+}
+
 long parse_algorithm_value(const char *value)
 {
 	if (!value)
@@ -452,6 +470,18 @@ int git_diff_ui_config(const char *var, const char *value,
 		return 0;
 	}
 
+	if (!strcmp(var, "diff.worddiff")) {
+		if (!value)
+			return config_error_nonbool(var);
+		diff_word_diff_default = parse_word_diff_value(value);
+		if (diff_word_diff_default < 0)
+			return error(_("unknown value for config '%s': %s"),
+				     var, value);
+		if (diff_word_diff_default == DIFF_WORDS_COLOR)
+			diff_use_color_default = 1;
+		return 0;
+	}
+
 	if (git_color_config(var, value, cb) < 0)
 		return -1;
 
@@ -4724,6 +4754,7 @@ void repo_diff_setup(struct repository *r, struct diff_options *options)
 	options->use_color = diff_use_color_default;
 	options->detect_rename = diff_detect_rename_default;
 	options->xdl_opts |= diff_algorithm;
+	options->word_diff |= diff_word_diff_default;
 	if (diff_indent_heuristic)
 		DIFF_XDL_SET(options, INDENT_HEURISTIC);
 
@@ -5504,21 +5535,18 @@ static int diff_opt_word_diff(const struct option *opt,
 			      const char *arg, int unset)
 {
 	struct diff_options *options = opt->value;
+	int value;
 
 	BUG_ON_OPT_NEG(unset);
+
 	if (arg) {
-		if (!strcmp(arg, "plain"))
-			options->word_diff = DIFF_WORDS_PLAIN;
-		else if (!strcmp(arg, "color")) {
-			options->use_color = 1;
-			options->word_diff = DIFF_WORDS_COLOR;
-		}
-		else if (!strcmp(arg, "porcelain"))
-			options->word_diff = DIFF_WORDS_PORCELAIN;
-		else if (!strcmp(arg, "none"))
-			options->word_diff = DIFF_WORDS_NONE;
-		else
+		value = parse_word_diff_value(arg);
+		if (value < 0)
 			return error(_("bad --word-diff argument: %s"), arg);
+		if (value == DIFF_WORDS_COLOR)
+			options->use_color = 1;
+
+		options->word_diff = value;
 	} else {
 		if (options->word_diff == DIFF_WORDS_NONE)
 			options->word_diff = DIFF_WORDS_PLAIN;
diff --git a/t/t4034-diff-words.sh b/t/t4034-diff-words.sh
index 4f70aa6e9f..2cc391c339 100755
--- a/t/t4034-diff-words.sh
+++ b/t/t4034-diff-words.sh
@@ -56,12 +56,19 @@ diff_with_opts () {
 	post=$(git rev-parse --short $(git hash-object post)) &&
 	test_must_fail git diff --no-index "$@" pre post >output &&
 	test_decode_color <output >output.decrypted &&
-	sed -e "2s/index [^ ]*/index $pre..$post/" expect >expected
+	sed -e "2s/index [^ ]*/index $pre..$post/" expect >expected &&
 	test_cmp expected output.decrypted
 }
 
 word_diff () {
-	diff_with_opts "--word-diff=$1" $(echo "$@" | cut -d' ' -s -f 2-)
+	# Capture the rest of the arguments to passthrough.
+	rest=$(echo "$@" | cut -d' ' -s -f 2-) &&
+	# Test via the config route.
+	git config diff.wordDiff $1 &&
+	diff_with_opts $rest &&
+	git config --unset diff.wordDiff &&
+	# Test via the command option route.
+	diff_with_opts "--word-diff=$1" $rest
 }
 
 test_language_driver () {
-- 
2.43.GIT