Merge branch 'jk/commit-buffer-length' into maint

A handful of code paths had to read the commit object more than
once when showing header fields that are usually not parsed.  The
internal data structure to keep track of the contents of the commit
object has been updated to reduce the need for this double-reading,
and to allow the caller find the length of the object.

* jk/commit-buffer-length:
  reuse cached commit buffer when parsing signatures
  commit: record buffer length in cache
  commit: convert commit->buffer to a slab
  commit-slab: provide a static initializer
  use get_commit_buffer everywhere
  convert logmsg_reencode to get_commit_buffer
  use get_commit_buffer to avoid duplicate code
  use get_cached_commit_buffer where appropriate
  provide helpers to access the commit buffer
  provide a helper to set the commit buffer
  provide a helper to free commit buffer
  sequencer: use logmsg_reencode in get_message
  logmsg_reencode: return const buffer
  do not create "struct commit" with xcalloc
  commit: push commit_index update into alloc_commit_node
  alloc: include any-object allocations in alloc_report
  replace dangerous uses of strbuf_attach
  commit_tree: take a pointer/len pair rather than a const strbuf

Author: gitster

alloc.c

@@ -47,23 +47,32 @@ union any_object {
 
 DEFINE_ALLOCATOR(blob, struct blob)
 DEFINE_ALLOCATOR(tree, struct tree)
-DEFINE_ALLOCATOR(commit, struct commit)
+DEFINE_ALLOCATOR(raw_commit, struct commit)
 DEFINE_ALLOCATOR(tag, struct tag)
 DEFINE_ALLOCATOR(object, union any_object)
 
+void *alloc_commit_node(void)
+{
+	static int commit_count;
+	struct commit *c = alloc_raw_commit_node();
+	c->index = commit_count++;
+	return c;
+}
+
 static void report(const char *name, unsigned int count, size_t size)
 {
 	fprintf(stderr, "%10s: %8u (%"PRIuMAX" kB)\n",
 			name, count, (uintmax_t) size);
 }
 
-#define REPORT(name)	\
-    report(#name, name##_allocs, name##_allocs * sizeof(struct name) >> 10)
+#define REPORT(name, type)	\
+    report(#name, name##_allocs, name##_allocs * sizeof(type) >> 10)
 
 void alloc_report(void)
 {
-	REPORT(blob);
-	REPORT(tree);
-	REPORT(commit);
-	REPORT(tag);
+	REPORT(blob, struct blob);
+	REPORT(tree, struct tree);
+	REPORT(raw_commit, struct commit);
+	REPORT(tag, struct tag);
+	REPORT(object, union any_object);
 }

builtin/blame.c

@@ -1405,7 +1405,7 @@ static void get_commit_info(struct commit *commit,
 {
 	int len;
 	const char *subject, *encoding;
-	char *message;
+	const char *message;
 
 	commit_info_init(ret);
 
@@ -1416,7 +1416,7 @@ static void get_commit_info(struct commit *commit,
 		    &ret->author_time, &ret->author_tz);
 
 	if (!detailed) {
-		logmsg_free(message, commit);
+		unuse_commit_buffer(commit, message);
 		return;
 	}
 
@@ -1430,7 +1430,7 @@ static void get_commit_info(struct commit *commit,
 	else
 		strbuf_addf(&ret->summary, "(%s)", sha1_to_hex(commit->object.sha1));
 
-	logmsg_free(message, commit);
+	unuse_commit_buffer(commit, message);
 }
 
 /*
@@ -2005,6 +2005,18 @@ static void append_merge_parents(struct commit_list **tail)
 	strbuf_release(&line);
 }
 
+/*
+ * This isn't as simple as passing sb->buf and sb->len, because we
+ * want to transfer ownership of the buffer to the commit (so we
+ * must use detach).
+ */
+static void set_commit_buffer_from_strbuf(struct commit *c, struct strbuf *sb)
+{
+	size_t len;
+	void *buf = strbuf_detach(sb, &len);
+	set_commit_buffer(c, buf, len);
+}
+
 /*
  * Prepare a dummy commit that represents the work tree (or staged) item.
  * Note that annotating work tree item never works in the reverse.
@@ -2026,7 +2038,7 @@ static struct commit *fake_working_tree_commit(struct diff_options *opt,
 	struct strbuf msg = STRBUF_INIT;
 
 	time(&now);
-	commit = xcalloc(1, sizeof(*commit));
+	commit = alloc_commit_node();
 	commit->object.parsed = 1;
 	commit->date = now;
 	commit->object.type = OBJ_COMMIT;
@@ -2053,7 +2065,7 @@ static struct commit *fake_working_tree_commit(struct diff_options *opt,
 		    ident, ident, path,
 		    (!contents_from ? path :
 		     (!strcmp(contents_from, "-") ? "standard input" : contents_from)));
-	commit->buffer = strbuf_detach(&msg, NULL);
+	set_commit_buffer_from_strbuf(commit, &msg);
 
 	if (!contents_from || strcmp("-", contents_from)) {
 		struct stat st;

builtin/commit-tree.c

@@ -123,8 +123,8 @@ int cmd_commit_tree(int argc, const char **argv, const char *prefix)
 			die_errno("git commit-tree: failed to read");
 	}
 
-	if (commit_tree(&buffer, tree_sha1, parents, commit_sha1,
-			NULL, sign_commit)) {
+	if (commit_tree(buffer.buf, buffer.len, tree_sha1, parents,
+			commit_sha1, NULL, sign_commit)) {
 		strbuf_release(&buffer);
 		return 1;
 	}

builtin/commit.c

@@ -1672,8 +1672,8 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 		append_merge_tag_headers(parents, &tail);
 	}
 
-	if (commit_tree_extended(&sb, active_cache_tree->sha1, parents, sha1,
-				 author_ident.buf, sign_commit, extra)) {
+	if (commit_tree_extended(sb.buf, sb.len, active_cache_tree->sha1,
+			 parents, sha1, author_ident.buf, sign_commit, extra)) {
 		rollback_index_files();
 		die(_("failed to write commit object"));
 	}

builtin/fast-export.c

@@ -279,6 +279,7 @@ static const char *find_encoding(const char *begin, const char *end)
 static void handle_commit(struct commit *commit, struct rev_info *rev)
 {
 	int saved_output_format = rev->diffopt.output_format;
+	const char *commit_buffer;
 	const char *author, *author_end, *committer, *committer_end;
 	const char *encoding, *message;
 	char *reencoded = NULL;
@@ -288,7 +289,8 @@ static void handle_commit(struct commit *commit, struct rev_info *rev)
 	rev->diffopt.output_format = DIFF_FORMAT_CALLBACK;
 
 	parse_commit_or_die(commit);
-	author = strstr(commit->buffer, "\nauthor ");
+	commit_buffer = get_commit_buffer(commit, NULL);
+	author = strstr(commit_buffer, "\nauthor ");
 	if (!author)
 		die ("Could not find author in commit %s",
 		     sha1_to_hex(commit->object.sha1));
@@ -335,6 +337,7 @@ static void handle_commit(struct commit *commit, struct rev_info *rev)
 			  ? strlen(message) : 0),
 	       reencoded ? reencoded : message ? message : "");
 	free(reencoded);
+	unuse_commit_buffer(commit, commit_buffer);
 
 	for (i = 0, p = commit->parents; p; p = p->next) {
 		int mark = get_object_mark(&p->item->object);

builtin/fmt-merge-msg.c

@@ -230,12 +230,14 @@ static void add_branch_desc(struct strbuf *out, const char *name)
 static void record_person(int which, struct string_list *people,
 			  struct commit *commit)
 {
+	const char *buffer;
 	char *name_buf, *name, *name_end;
 	struct string_list_item *elem;
 	const char *field;
 
 	field = (which == 'a') ? "\nauthor " : "\ncommitter ";
-	name = strstr(commit->buffer, field);
+	buffer = get_commit_buffer(commit, NULL);
+	name = strstr(buffer, field);
 	if (!name)
 		return;
 	name += strlen(field);
@@ -247,6 +249,7 @@ static void record_person(int which, struct string_list *people,
 	if (name_end < name)
 		return;
 	name_buf = xmemdupz(name, name_end - name + 1);
+	unuse_commit_buffer(commit, buffer);
 
 	elem = string_list_lookup(people, name_buf);
 	if (!elem) {

builtin/fsck.c

@@ -310,8 +310,7 @@ static int fsck_obj(struct object *obj)
 	if (obj->type == OBJ_COMMIT) {
 		struct commit *commit = (struct commit *) obj;
 
-		free(commit->buffer);
-		commit->buffer = NULL;
+		free_commit_buffer(commit);
 
 		if (!commit->parents && show_root)
 			printf("root %s\n", sha1_to_hex(commit->object.sha1));

builtin/index-pack.c

@@ -786,7 +786,8 @@ static void sha1_object(const void *data, struct object_entry *obj_entry,
 			}
 			if (obj->type == OBJ_COMMIT) {
 				struct commit *commit = (struct commit *) obj;
-				commit->buffer = NULL;
+				if (detach_commit_buffer(commit, NULL) != data)
+					die("BUG: parse_object_buffer transmogrified our buffer");
 			}
 			obj->flags |= FLAG_CHECKED;
 		}

builtin/log.c

@@ -345,8 +345,7 @@ static int cmd_log_walk(struct rev_info *rev)
 			rev->max_count++;
 		if (!rev->reflog_info) {
 			/* we allow cycles in reflog ancestry */
-			free(commit->buffer);
-			commit->buffer = NULL;
+			free_commit_buffer(commit);
 		}
 		free_commit_list(commit->parents);
 		commit->parents = NULL;
@@ -915,9 +914,12 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 	log_write_email_headers(rev, head, &pp.subject, &pp.after_subject,
 				&need_8bit_cte);
 
-	for (i = 0; !need_8bit_cte && i < nr; i++)
-		if (has_non_ascii(list[i]->buffer))
+	for (i = 0; !need_8bit_cte && i < nr; i++) {
+		const char *buf = get_commit_buffer(list[i], NULL);
+		if (has_non_ascii(buf))
 			need_8bit_cte = 1;
+		unuse_commit_buffer(list[i], buf);
+	}
 
 	if (!branch_name)
 		branch_name = find_branch_name(rev);
@@ -1504,8 +1506,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		    reopen_stdout(rev.numbered_files ? NULL : commit, NULL, &rev, quiet))
 			die(_("Failed to create output files"));
 		shown = log_tree_commit(&rev, commit);
-		free(commit->buffer);
-		commit->buffer = NULL;
+		free_commit_buffer(commit);
 
 		/* We put one extra blank line between formatted
 		 * patches and this flag is used by log-tree code

builtin/merge.c

@@ -852,8 +852,8 @@ static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 	parent->next->item = remoteheads->item;
 	parent->next->next = NULL;
 	prepare_to_commit(remoteheads);
-	if (commit_tree(&merge_msg, result_tree, parent, result_commit, NULL,
-			sign_commit))
+	if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parent,
+			result_commit, NULL, sign_commit))
 		die(_("failed to write commit object"));
 	finish(head, remoteheads, result_commit, "In-index merge");
 	drop_save();
@@ -877,8 +877,8 @@ static int finish_automerge(struct commit *head,
 		commit_list_insert(head, &parents);
 	strbuf_addch(&merge_msg, '\n');
 	prepare_to_commit(remoteheads);
-	if (commit_tree(&merge_msg, result_tree, parents, result_commit,
-			NULL, sign_commit))
+	if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
+			result_commit, NULL, sign_commit))
 		die(_("failed to write commit object"));
 	strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 	finish(head, remoteheads, result_commit, buf.buf);