Enable the creation of transient cache entries

Signed-off-by: Jameson Miller <jamill@microsoft.com>

builtin/checkout.c

@@ -236,11 +236,11 @@ static int checkout_merged(int pos, const struct checkout *state)
 			    blob_type, oid.hash))
 		die(_("Unable to add merge result for '%s'"), path);
 	free(result_buf.ptr);
-	ce = make_cache_entry_from_index(state->istate, mode, oid.hash, path, 2, 0);
+	ce = make_transient_cache_entry(mode, oid.hash, path, 2);
 	if (!ce)
 		die(_("make_cache_entry failed for path '%s'"), path);
 	status = checkout_entry(ce, state, NULL);
-	cache_entry_free(ce);
+	transient_cache_entry_free(ce);
 	return status;
 }
 

builtin/difftool.c

@@ -321,28 +321,10 @@ static int checkout_path(unsigned mode, struct object_id *oid,
 	struct cache_entry *ce;
 	int ret;
 
-	/*
-	 * REVIEW: This is a transient cache entry - it is freed
-	 *         a couple lines below.
-	 *
-	 *         We have worked to remove the ability to
-	 *         allocate individual cache entries -
-	 *         but if we know it is going to be freed,
-	 *         then maybe there is no need to allocate
-	 *         from a memory pool.
-	 *
-	 *         For now, allocate from the_index.
-	 *
-	 *         Options:
-	 *         1) expect an istate to be passed in (via state)
-	 *         2) (re)enable us to allocate an individual cache entry
-	 *         3) work against the_index
-	 *         4) Can we use stack allocated memory?
-	 */
-	ce = make_cache_entry_from_index(&the_index, mode, oid->hash, path, 0, 0);
+	ce = make_transient_cache_entry(mode, oid->hash, path, 0);
 	ret = checkout_entry(ce, state, NULL);
 
-	cache_entry_free(ce);
+	transient_cache_entry_free(ce);
 	return ret;
 }
 

cache.h

@@ -716,14 +716,24 @@ extern int add_to_index(struct index_state *, const char *path, struct stat *, i
 extern int add_file_to_index(struct index_state *, const char *path, int flags);
 
 extern struct cache_entry *make_cache_entry_from_index(struct index_state *, unsigned int mode, const unsigned char *sha1, const char *path, int stage, unsigned int refresh_options);
+extern struct cache_entry *make_transient_cache_entry(unsigned int mode, const unsigned char *sha1, const char *path, int stage);
 
 /*
- * Create an empty cache entry struct.
+ * Create an empty cache entry struct. This is intended for use with
+ * cache_entries that could be added to the associated index.
  *
  * istate: The index whose memory pool this cache entry should be allocated from.
  * len: The length to reserve for the path field of the cache entry.
  */
 extern struct cache_entry *make_empty_cache_entry_from_index(struct index_state *istate, size_t len);
+
+/*
+ * Create an empty cache entry struct. This is intended for use with
+ * cache_entries that will not be added to an index.
+ *
+ * len: The length to reserve for the path field of the cache entry.
+ */
+extern struct cache_entry *make_empty_transient_cache_entry(size_t len);
 extern int chmod_index_entry(struct index_state *, struct cache_entry *ce, char flip);
 extern int ce_same_name(const struct cache_entry *a, const struct cache_entry *b);
 extern void set_object_name_for_intent_to_add_entry(struct cache_entry *ce);
@@ -2000,6 +2010,8 @@ void safe_create_dir(const char *dir, int share);
 extern int print_sha1_ellipsis(void);
 
 void cache_entry_free(struct cache_entry *ce);
+void transient_cache_entry_free(struct cache_entry *ce);
+
 void validate_cache_entries(const struct index_state *istate);
 
 #endif /* CACHE_H */

read-cache.c

@@ -781,10 +781,15 @@ struct cache_entry *make_empty_cache_entry_from_index(struct index_state *istate
 	return mem_pool__ce_calloc(find_mem_pool(istate), len);
 }
 
-struct cache_entry *make_cache_entry_from_index(struct index_state *istate,
-						unsigned int mode,
-						const unsigned char *sha1, const char *path, int stage,
-						unsigned int refresh_options)
+struct cache_entry *make_empty_transient_cache_entry(size_t len)
+{
+	return xcalloc(1, cache_entry_size(len));
+}
+
+struct cache_entry *make_cache_entry(struct index_state *istate,
+		 unsigned int mode,
+		 const unsigned char *sha1, const char *path, int stage,
+		 unsigned int refresh_options, int is_transient)
 {
 	int len;
 	struct cache_entry *ce, *ret;
@@ -795,20 +800,45 @@ struct cache_entry *make_cache_entry_from_index(struct index_state *istate,
 	}
 
 	len = strlen(path);
-	ce = make_empty_cache_entry_from_index(istate, len);
+	ce = is_transient ? make_empty_transient_cache_entry(len) :
+			    make_empty_cache_entry_from_index(istate, len);
 
 	hashcpy(ce->oid.hash, sha1);
 	memcpy(ce->name, path, len);
 	ce->ce_flags = create_ce_flags(stage);
 	ce->ce_namelen = len;
 	ce->ce_mode = create_ce_mode(mode);
 
-	ret = refresh_cache_entry(istate, ce, refresh_options);
-	if (ret != ce)
-		cache_entry_free(ce);
+	/*
+	 * Transient cache entries cannot be refreshed - they are not associated
+	 * with the index.
+	 */
+	if (!is_transient) {
+		ret = refresh_cache_entry(istate, ce, refresh_options);
+
+		if (ret != ce)
+			cache_entry_free(ce);
+	} else {
+		ret = ce;
+	}
+
 	return ret;
 }
 
+struct cache_entry *make_cache_entry_from_index(struct index_state *istate, unsigned int mode,
+			    const unsigned char *sha1, const char *path,
+			    int stage, unsigned int refresh_options)
+{
+	return make_cache_entry(istate, mode, sha1, path, stage,
+				refresh_options, 0);
+}
+
+struct cache_entry *make_transient_cache_entry(unsigned int mode, const unsigned char *sha1,
+			   const char *path, int stage)
+{
+	return make_cache_entry(NULL, mode, sha1, path, stage, 0, 1);
+}
+
 /*
  * Chmod an index entry with either +x or -x.
  *
@@ -2830,3 +2860,8 @@ void cache_entry_free(struct cache_entry *ce)
 	if (ce && invalidate_cache_entry)
 		memset(ce, 0xCD, cache_entry_size(ce->ce_namelen));
 }
+
+void transient_cache_entry_free(struct cache_entry *ce)
+{
+	free(ce);
+}

unpack-trees.c

@@ -781,10 +781,14 @@ static int ce_in_traverse_path(const struct cache_entry *ce,
 static struct cache_entry *create_ce_entry(const struct traverse_info *info,
 	const struct name_entry *n,
 	int stage,
-	struct index_state *istate)
+	struct index_state *istate,
+	int is_transient)
 {
 	int len = traverse_path_len(info, n);
-	struct cache_entry *ce = make_empty_cache_entry_from_index(istate, len);
+	struct cache_entry *ce =
+		is_transient ?
+		make_empty_transient_cache_entry(len) :
+		make_empty_cache_entry_from_index(istate, len);
 
 	ce->ce_mode = create_ce_mode(n->mode);
 	ce->ce_flags = create_ce_flags(stage);
@@ -830,7 +834,7 @@ static int unpack_nondirectories(int n, unsigned long mask,
 			stage = 3;
 		else
 			stage = 2;
-		src[i + o->merge] = create_ce_entry(info, names + i, stage, &o->result);
+		src[i + o->merge] = create_ce_entry(info, names + i, stage, &o->result, o->merge);
 	}
 
 	if (o->merge) {
@@ -839,7 +843,7 @@ static int unpack_nondirectories(int n, unsigned long mask,
 		for (i = 0; i < n; i++) {
 			struct cache_entry *ce = src[i + o->merge];
 			if (ce != o->df_conflict_entry)
-				cache_entry_free(ce);
+				transient_cache_entry_free(ce);
 		}
 		return rc;
 	}