Merge branch 'jt/avoid-prefetch-when-able-in-diff'

"git diff" in a partial clone learned to avoid lazy loading blob
objects in more casese when they are not needed.

* jt/avoid-prefetch-when-able-in-diff:
  diff: restrict when prefetching occurs
  diff: refactor object read
  diff: make diff_populate_filespec_options struct
  promisor-remote: accept 0 as oid_nr in function

1 files changed, 57 insertions, 7 deletions

diff --git a/diffcore-rename.c b/diffcore-rename.c
index e189f407af..99e63e90f8 100644
--- a/diffcore-rename.c
+++ b/diffcore-rename.c
@@ -1,4 +1,5 @@
 /*
+ *
  * Copyright (C) 2005 Junio C Hamano
  */
 #include "cache.h"
@@ -7,6 +8,7 @@
 #include "object-store.h"
 #include "hashmap.h"
 #include "progress.h"
+#include "promisor-remote.h"
 
 /* Table of rename/copy destinations */
 
@@ -128,10 +130,46 @@ struct diff_score {
 	short name_score;
 };
 
+struct prefetch_options {
+	struct repository *repo;
+	int skip_unmodified;
+};
+static void prefetch(void *prefetch_options)
+{
+	struct prefetch_options *options = prefetch_options;
+	int i;
+	struct oid_array to_fetch = OID_ARRAY_INIT;
+
+	for (i = 0; i < rename_dst_nr; i++) {
+		if (rename_dst[i].pair)
+			/*
+			 * The loop in diffcore_rename() will not need these
+			 * blobs, so skip prefetching.
+			 */
+			continue; /* already found exact match */
+		diff_add_if_missing(options->repo, &to_fetch,
+				    rename_dst[i].two);
+	}
+	for (i = 0; i < rename_src_nr; i++) {
+		if (options->skip_unmodified &&
+		    diff_unmodified_pair(rename_src[i].p))
+			/*
+			 * The loop in diffcore_rename() will not need these
+			 * blobs, so skip prefetching.
+			 */
+			continue;
+		diff_add_if_missing(options->repo, &to_fetch,
+				    rename_src[i].p->one);
+	}
+	promisor_remote_get_direct(options->repo, to_fetch.oid, to_fetch.nr);
+	oid_array_clear(&to_fetch);
+}
+
 static int estimate_similarity(struct repository *r,
 			       struct diff_filespec *src,
 			       struct diff_filespec *dst,
-			       int minimum_score)
+			       int minimum_score,
+			       int skip_unmodified)
 {
 	/* src points at a file that existed in the original tree (or
 	 * optionally a file in the destination tree) and dst points
@@ -148,6 +186,15 @@ static int estimate_similarity(struct repository *r,
 	 */
 	unsigned long max_size, delta_size, base_size, src_copied, literal_added;
 	int score;
+	struct diff_populate_filespec_options dpf_options = {
+		.check_size_only = 1
+	};
+	struct prefetch_options prefetch_options = {r, skip_unmodified};
+
+	if (r == the_repository && has_promisor_remote()) {
+		dpf_options.missing_object_cb = prefetch;
+		dpf_options.missing_object_data = &prefetch_options;
+	}
 
 	/* We deal only with regular files.  Symlink renames are handled
 	 * only when they are exact matches --- in other words, no edits
@@ -166,10 +213,10 @@ static int estimate_similarity(struct repository *r,
 	 * say whether the size is valid or not!)
 	 */
 	if (!src->cnt_data &&
-	    diff_populate_filespec(r, src, CHECK_SIZE_ONLY))
+	    diff_populate_filespec(r, src, &dpf_options))
 		return 0;
 	if (!dst->cnt_data &&
-	    diff_populate_filespec(r, dst, CHECK_SIZE_ONLY))
+	    diff_populate_filespec(r, dst, &dpf_options))
 		return 0;
 
 	max_size = ((src->size > dst->size) ? src->size : dst->size);
@@ -187,9 +234,11 @@ static int estimate_similarity(struct repository *r,
 	if (max_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
 		return 0;
 
-	if (!src->cnt_data && diff_populate_filespec(r, src, 0))
+	dpf_options.check_size_only = 0;
+
+	if (!src->cnt_data && diff_populate_filespec(r, src, &dpf_options))
 		return 0;
-	if (!dst->cnt_data && diff_populate_filespec(r, dst, 0))
+	if (!dst->cnt_data && diff_populate_filespec(r, dst, &dpf_options))
 		return 0;
 
 	if (diffcore_count_changes(r, src, dst,
@@ -261,7 +310,7 @@ static unsigned int hash_filespec(struct repository *r,
 				  struct diff_filespec *filespec)
 {
 	if (!filespec->oid_valid) {
-		if (diff_populate_filespec(r, filespec, 0))
+		if (diff_populate_filespec(r, filespec, NULL))
 			return 0;
 		hash_object_file(r->hash_algo, filespec->data, filespec->size,
 				 "blob", &filespec->oid);
@@ -566,7 +615,8 @@ void diffcore_rename(struct diff_options *options)
 
 			this_src.score = estimate_similarity(options->repo,
 							     one, two,
-							     minimum_score);
+							     minimum_score,
+							     skip_unmodified);
 			this_src.name_score = basename_same(one, two);
 			this_src.dst = i;
 			this_src.src = j;