[PATCH 4/5] scalar: teach `diagnose` to gather loose objects information

["Matthew John Cheetham via GitGitGadget" <gitgitgadget@xxxxxxxxx>]

From: Matthew John Cheetham <mjcheetham@xxxxxxxxxxx>

When operating at the scale that Scalar wants to support, certain data
shapes are more likely to cause undesirable performance issues, such as
large numbers or large sizes of loose objects.

By including statistics about this, `scalar diagnose` now makes it
easier to identify such scenarios.

Signed-off-by: Matthew John Cheetham <mjcheetham@xxxxxxxxxxx>
---
 contrib/scalar/scalar.c          | 60 ++++++++++++++++++++++++++++++++
 contrib/scalar/t/t9099-scalar.sh |  2 ++
 2 files changed, 62 insertions(+)

diff --git a/contrib/scalar/scalar.c b/contrib/scalar/scalar.c
index 690933ffdf3..c0ad4948215 100644
--- a/contrib/scalar/scalar.c
+++ b/contrib/scalar/scalar.c
@@ -686,6 +686,60 @@ static void dir_file_stats(struct strbuf *buf, const char *path)
 	closedir(dir);
 }
 
+static int count_files(char *path)
+{
+	DIR *dir = opendir(path);
+	struct dirent *e;
+	int count = 0;
+
+	if (!dir)
+		return 0;
+
+	while ((e = readdir(dir)) != NULL)
+		if (!is_dot_or_dotdot(e->d_name) && e->d_type == DT_REG)
+			count++;
+
+	closedir(dir);
+	return count;
+}
+
+static void loose_objs_stats(struct strbuf *buf, const char *path)
+{
+	DIR *dir = opendir(path);
+	struct dirent *e;
+	int count;
+	int total = 0;
+	unsigned char c;
+	struct strbuf count_path = STRBUF_INIT;
+	size_t base_path_len;
+
+	if (!dir)
+		return;
+
+	strbuf_addstr(buf, "Object directory stats for ");
+	strbuf_add_absolute_path(buf, path);
+	strbuf_addstr(buf, ":\n");
+
+	strbuf_add_absolute_path(&count_path, path);
+	strbuf_addch(&count_path, '/');
+	base_path_len = count_path.len;
+
+	while ((e = readdir(dir)) != NULL)
+		if (!is_dot_or_dotdot(e->d_name) &&
+		    e->d_type == DT_DIR && strlen(e->d_name) == 2 &&
+		    !hex_to_bytes(&c, e->d_name, 1)) {
+			strbuf_setlen(&count_path, base_path_len);
+			strbuf_addstr(&count_path, e->d_name);
+			total += (count = count_files(count_path.buf));
+			strbuf_addf(buf, "%s : %7d files\n", e->d_name, count);
+		}
+
+	strbuf_addf(buf, "Total: %d loose objects", total);
+
+	strbuf_release(&count_path);
+	closedir(dir);
+}
+
 static int cmd_diagnose(int argc, const char **argv)
 {
 	struct option options[] = {
@@ -734,6 +788,12 @@ static int cmd_diagnose(int argc, const char **argv)
 	if ((res = stage(tmp_dir.buf, &buf, "packs-local.txt")))
 		goto diagnose_cleanup;
 
+	strbuf_reset(&buf);
+	loose_objs_stats(&buf, ".git/objects");
+
+	if ((res = stage(tmp_dir.buf, &buf, "objects-local.txt")))
+		goto diagnose_cleanup;
+
 	if ((res = stage_directory(tmp_dir.buf, ".git", 0)) ||
 	    (res = stage_directory(tmp_dir.buf, ".git/hooks", 0)) ||
 	    (res = stage_directory(tmp_dir.buf, ".git/info", 0)) ||
diff --git a/contrib/scalar/t/t9099-scalar.sh b/contrib/scalar/t/t9099-scalar.sh
index b1745851e31..f2ec156d819 100755
--- a/contrib/scalar/t/t9099-scalar.sh
+++ b/contrib/scalar/t/t9099-scalar.sh
@@ -77,6 +77,8 @@ test_expect_success UNZIP 'scalar diagnose' '
 	unzip -p "$zip_path" diagnostics.log >out &&
 	test_file_not_empty out &&
 	unzip -p "$zip_path" packs-local.txt >out &&
+	test_file_not_empty out &&
+	unzip -p "$zip_path" objects-local.txt >out &&
 	test_file_not_empty out
 '
 
-- 
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