Teach diff --submodule that modified submodule directory is dirty

Since commit 8e08b4 git diff does append "-dirty" to the work tree side
if the working directory of a submodule contains new or modified files.
Lets do the same when the --submodule option is used.

Signed-off-by: Jens Lehmann <Jens.Lehmann@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff.c

@@ -1615,7 +1615,7 @@ static void builtin_diff(const char *name_a,
 		const char *del = diff_get_color_opt(o, DIFF_FILE_OLD);
 		const char *add = diff_get_color_opt(o, DIFF_FILE_NEW);
 		show_submodule_summary(o->file, one ? one->path : two->path,
-				one->sha1, two->sha1,
+				one->sha1, two->sha1, two->dirty_submodule,
 				del, add, reset);
 		return;
 	}

submodule.c

@@ -36,6 +36,7 @@ static int add_submodule_odb(const char *path)
 
 void show_submodule_summary(FILE *f, const char *path,
 		unsigned char one[20], unsigned char two[20],
+		unsigned dirty_submodule,
 		const char *del, const char *add, const char *reset)
 {
 	struct rev_info rev;
@@ -85,6 +86,8 @@ void show_submodule_summary(FILE *f, const char *path,
 	if (!fast_backward && !fast_forward)
 		strbuf_addch(&sb, '.');
 	strbuf_addf(&sb, "%s", find_unique_abbrev(two, DEFAULT_ABBREV));
+	if (dirty_submodule)
+		strbuf_add(&sb, "-dirty", 6);
 	if (message)
 		strbuf_addf(&sb, " %s\n", message);
 	else

submodule.h

@@ -3,6 +3,7 @@
 
 void show_submodule_summary(FILE *f, const char *path,
 		unsigned char one[20], unsigned char two[20],
+		unsigned dirty_submodule,
 		const char *del, const char *add, const char *reset);
 int is_submodule_modified(const char *path);
 

t/t4041-diff-submodule.sh

@@ -191,6 +191,73 @@ EOF
 "
 
 commit_file sm1 &&
+test_expect_success 'submodule is up to date' "
+	git diff-index -p --submodule=log HEAD >actual &&
+	diff actual - <<-EOF
+EOF
+"
+
+test_expect_success 'submodule contains untracked content' "
+	echo new > sm1/new-file &&
+	git diff-index -p --submodule=log HEAD >actual &&
+	diff actual - <<-EOF
+Submodule sm1 $head6..$head6-dirty:
+EOF
+"
+
+test_expect_success 'submodule contains untracked and modifed content' "
+	echo new > sm1/foo6 &&
+	git diff-index -p --submodule=log HEAD >actual &&
+	diff actual - <<-EOF
+Submodule sm1 $head6..$head6-dirty:
+EOF
+"
+
+test_expect_success 'submodule contains modifed content' "
+	rm -f sm1/new-file &&
+	git diff-index -p --submodule=log HEAD >actual &&
+	diff actual - <<-EOF
+Submodule sm1 $head6..$head6-dirty:
+EOF
+"
+
+(cd sm1; git commit -mchange foo6 >/dev/null) &&
+head8=$(cd sm1; git rev-parse --verify HEAD | cut -c1-7) &&
+test_expect_success 'submodule is modified' "
+	git diff-index -p --submodule=log HEAD >actual &&
+	diff actual - <<-EOF
+Submodule sm1 $head6..$head8:
+  > change
+EOF
+"
+
+test_expect_success 'modified submodule contains untracked content' "
+	echo new > sm1/new-file &&
+	git diff-index -p --submodule=log HEAD >actual &&
+	diff actual - <<-EOF
+Submodule sm1 $head6..$head8-dirty:
+  > change
+EOF
+"
+
+test_expect_success 'modified submodule contains untracked and modifed content' "
+	echo modification >> sm1/foo6 &&
+	git diff-index -p --submodule=log HEAD >actual &&
+	diff actual - <<-EOF
+Submodule sm1 $head6..$head8-dirty:
+  > change
+EOF
+"
+
+test_expect_success 'modified submodule contains modifed content' "
+	rm -f sm1/new-file &&
+	git diff-index -p --submodule=log HEAD >actual &&
+	diff actual - <<-EOF
+Submodule sm1 $head6..$head8-dirty:
+  > change
+EOF
+"
+
 rm -rf sm1
 test_expect_success 'deleted submodule' "
 	git diff-index -p --submodule=log HEAD >actual &&