survey: add report of "largest" paths

Since we are already walking our reachable objects using the path-walk API,
let's now collect lists of the paths that contribute most to different
metrics. Specifically, we care about

 * Number of versions.
 * Total size on disk.
 * Total inflated size (no delta or zlib compression).

This information can be critical to discovering which parts of the
repository are causing the most growth, especially on-disk size. Different
packing strategies might help compress data more efficiently, but the toal
inflated size is a representation of the raw size of all snapshots of those
paths. Even when stored efficiently on disk, that size represents how much
information must be processed to complete a command such as 'git blame'.

Since the on-disk size is likely to be fragile, stop testing the exact
output of 'git survey' and check that the correct set of headers is
output.

Signed-off-by: Derrick Stolee <stolee@gmail.com>

Author: derrickstolee

builtin/survey.c

@@ -80,7 +80,6 @@ struct survey_report_object_size_summary {
 
 typedef int (*survey_top_cmp)(void *v1, void *v2);
 
-MAYBE_UNUSED
 static int cmp_by_nr(void *v1, void *v2)
 {
 	struct survey_report_object_size_summary *s1 = v1;
@@ -93,7 +92,6 @@ static int cmp_by_nr(void *v1, void *v2)
 	return 0;
 }
 
-MAYBE_UNUSED
 static int cmp_by_disk_size(void *v1, void *v2)
 {
 	struct survey_report_object_size_summary *s1 = v1;
@@ -106,7 +104,6 @@ static int cmp_by_disk_size(void *v1, void *v2)
 	return 0;
 }
 
-MAYBE_UNUSED
 static int cmp_by_inflated_size(void *v1, void *v2)
 {
 	struct survey_report_object_size_summary *s1 = v1;
@@ -137,7 +134,6 @@ struct survey_report_top_table {
 	void *data;
 };
 
-MAYBE_UNUSED
 static void init_top_sizes(struct survey_report_top_table *top,
 			   size_t limit, const char *name,
 			   survey_top_cmp cmp)
@@ -163,7 +159,6 @@ static void clear_top_sizes(struct survey_report_top_table *top)
 	free(sz_array);
 }
 
-MAYBE_UNUSED
 static void maybe_insert_into_top_size(struct survey_report_top_table *top,
 				       struct survey_report_object_size_summary *summary)
 {
@@ -200,6 +195,10 @@ struct survey_report {
 	struct survey_report_object_summary reachable_objects;
 
 	struct survey_report_object_size_summary *by_type;
+
+	struct survey_report_top_table *top_paths_by_count;
+	struct survey_report_top_table *top_paths_by_disk;
+	struct survey_report_top_table *top_paths_by_inflate;
 };
 
 #define REPORT_TYPE_COMMIT 0
@@ -451,6 +450,13 @@ static void survey_report_object_sizes(const char *title,
 	clear_table(&table);
 }
 
+static void survey_report_plaintext_sorted_size(
+		struct survey_report_top_table *top)
+{
+	survey_report_object_sizes(top->name,  _("Path"),
+				   top->data, top->nr);
+}
+
 static void survey_report_plaintext(struct survey_context *ctx)
 {
 	printf("GIT SURVEY for \"%s\"\n", ctx->repo->worktree);
@@ -461,6 +467,21 @@ static void survey_report_plaintext(struct survey_context *ctx)
 				   _("Object Type"),
 				   ctx->report.by_type,
 				   REPORT_TYPE_COUNT);
+
+	survey_report_plaintext_sorted_size(
+		&ctx->report.top_paths_by_count[REPORT_TYPE_TREE]);
+	survey_report_plaintext_sorted_size(
+		&ctx->report.top_paths_by_count[REPORT_TYPE_BLOB]);
+
+	survey_report_plaintext_sorted_size(
+		&ctx->report.top_paths_by_disk[REPORT_TYPE_TREE]);
+	survey_report_plaintext_sorted_size(
+		&ctx->report.top_paths_by_disk[REPORT_TYPE_BLOB]);
+
+	survey_report_plaintext_sorted_size(
+		&ctx->report.top_paths_by_inflate[REPORT_TYPE_TREE]);
+	survey_report_plaintext_sorted_size(
+		&ctx->report.top_paths_by_inflate[REPORT_TYPE_BLOB]);
 }
 
 /*
@@ -701,7 +722,8 @@ static void increment_totals(struct survey_context *ctx,
 
 static void increment_object_totals(struct survey_context *ctx,
 				    struct oid_array *oids,
-				    enum object_type type)
+				    enum object_type type,
+				    const char *path)
 {
 	struct survey_report_object_size_summary *total;
 	struct survey_report_object_size_summary summary = { 0 };
@@ -733,9 +755,30 @@ static void increment_object_totals(struct survey_context *ctx,
 	total->disk_size += summary.disk_size;
 	total->inflated_size += summary.inflated_size;
 	total->num_missing += summary.num_missing;
+
+	if (type == OBJ_TREE || type == OBJ_BLOB) {
+		int index = type == OBJ_TREE ?
+			    REPORT_TYPE_TREE : REPORT_TYPE_BLOB;
+		struct survey_report_top_table *top;
+
+		/*
+		 * Temporarily store (const char *) here, but it will
+		 * be duped if inserted and will not be freed.
+		 */
+		summary.label = (char *)path;
+
+		top = ctx->report.top_paths_by_count;
+		maybe_insert_into_top_size(&top[index], &summary);
+
+		top = ctx->report.top_paths_by_disk;
+		maybe_insert_into_top_size(&top[index], &summary);
+
+		top = ctx->report.top_paths_by_inflate;
+		maybe_insert_into_top_size(&top[index], &summary);
+	}
 }
 
-static int survey_objects_path_walk_fn(const char *path UNUSED,
+static int survey_objects_path_walk_fn(const char *path,
 				       struct oid_array *oids,
 				       enum object_type type,
 				       void *data)
@@ -744,7 +787,7 @@ static int survey_objects_path_walk_fn(const char *path UNUSED,
 
 	increment_object_counts(&ctx->report.reachable_objects,
 				type, oids->nr);
-	increment_object_totals(ctx, oids, type);
+	increment_object_totals(ctx, oids, type, path);
 
 	ctx->progress_nr += oids->nr;
 	display_progress(ctx->progress, ctx->progress_nr);
@@ -754,11 +797,31 @@ static int survey_objects_path_walk_fn(const char *path UNUSED,
 
 static void initialize_report(struct survey_context *ctx)
 {
+	const int top_limit = 100;
+
 	CALLOC_ARRAY(ctx->report.by_type, REPORT_TYPE_COUNT);
 	ctx->report.by_type[REPORT_TYPE_COMMIT].label = xstrdup(_("Commits"));
 	ctx->report.by_type[REPORT_TYPE_TREE].label = xstrdup(_("Trees"));
 	ctx->report.by_type[REPORT_TYPE_BLOB].label = xstrdup(_("Blobs"));
 	ctx->report.by_type[REPORT_TYPE_TAG].label = xstrdup(_("Tags"));
+
+	CALLOC_ARRAY(ctx->report.top_paths_by_count, REPORT_TYPE_COUNT);
+	init_top_sizes(&ctx->report.top_paths_by_count[REPORT_TYPE_TREE],
+		       top_limit, _("TOP DIRECTORIES BY COUNT"), cmp_by_nr);
+	init_top_sizes(&ctx->report.top_paths_by_count[REPORT_TYPE_BLOB],
+		       top_limit, _("TOP FILES BY COUNT"), cmp_by_nr);
+
+	CALLOC_ARRAY(ctx->report.top_paths_by_disk, REPORT_TYPE_COUNT);
+	init_top_sizes(&ctx->report.top_paths_by_disk[REPORT_TYPE_TREE],
+		       top_limit, _("TOP DIRECTORIES BY DISK SIZE"), cmp_by_disk_size);
+	init_top_sizes(&ctx->report.top_paths_by_disk[REPORT_TYPE_BLOB],
+		       top_limit, _("TOP FILES BY DISK SIZE"), cmp_by_disk_size);
+
+	CALLOC_ARRAY(ctx->report.top_paths_by_inflate, REPORT_TYPE_COUNT);
+	init_top_sizes(&ctx->report.top_paths_by_inflate[REPORT_TYPE_TREE],
+		       top_limit, _("TOP DIRECTORIES BY INFLATED SIZE"), cmp_by_inflated_size);
+	init_top_sizes(&ctx->report.top_paths_by_inflate[REPORT_TYPE_BLOB],
+		       top_limit, _("TOP FILES BY INFLATED SIZE"), cmp_by_inflated_size);
 }
 
 static void survey_phase_objects(struct survey_context *ctx)

t/t8100-git-survey.sh

@@ -81,7 +81,17 @@ test_expect_success 'git survey (default)' '
 	       Tags |     4 | $(test_oid tags_size_on_disk) | $(test_oid tags_size)
 	EOF
 
-	test_cmp expect out
+	lines=$(wc -l <expect) &&
+	head -n $lines out >out-trimmed &&
+	test_cmp expect out-trimmed &&
+
+	for type in "DIRECTORIES" "FILES"
+	do
+		for metric in "COUNT" "DISK SIZE" "INFLATED SIZE"
+		do
+			grep "TOP $type BY $metric" out || return 1
+		done || return 1
+	done
 '
 
 test_done