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

11 files changed, 47 insertions, 29 deletions

diff --git a/builtin/blame.c b/builtin/blame.c
index d8b276048..ef7cb1d25 100644
--- a/builtin/blame.c
+++ b/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);
 }
 
 /*
@@ -2006,6 +2006,18 @@ static void append_merge_parents(struct commit_list **tail)
 }
 
 /*
+ * 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;
diff --git a/builtin/commit-tree.c b/builtin/commit-tree.c
index 987a4c3d7..8a66c74e0 100644
--- a/builtin/commit-tree.c
+++ b/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;
 	}
diff --git a/builtin/commit.c b/builtin/commit.c
index 12afc42d1..39cf8976e 100644
--- a/builtin/commit.c
+++ b/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"));
 	}
diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index b8d8a3aaf..05d161f19 100644
--- a/builtin/fast-export.c
+++ b/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);
diff --git a/builtin/fmt-merge-msg.c b/builtin/fmt-merge-msg.c
index 3906eda87..ef8b254ef 100644
--- a/builtin/fmt-merge-msg.c
+++ b/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) {
diff --git a/builtin/fsck.c b/builtin/fsck.c
index fc150c882..8aadca160 100644
--- a/builtin/fsck.c
+++ b/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));
diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index 18f57de58..8b3bd29db 100644
--- a/builtin/index-pack.c
+++ b/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;
 		}
diff --git a/builtin/log.c b/builtin/log.c
index 3b6a6bbad..4f678136d 100644
--- a/builtin/log.c
+++ b/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
diff --git a/builtin/merge.c b/builtin/merge.c
index 66d884330..8763b2efa 100644
--- a/builtin/merge.c
+++ b/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);
diff --git a/builtin/reset.c b/builtin/reset.c
index f4e087596..6bd624582 100644
--- a/builtin/reset.c
+++ b/builtin/reset.c
@@ -93,7 +93,7 @@ static int reset_index(const unsigned char *sha1, int reset_type, int quiet)
 static void print_new_head_line(struct commit *commit)
 {
 	const char *hex, *body;
-	char *msg;
+	const char *msg;
 
 	hex = find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV);
 	printf(_("HEAD is now at %s"), hex);
@@ -109,7 +109,7 @@ static void print_new_head_line(struct commit *commit)
 	}
 	else
 		printf("\n");
-	logmsg_free(msg, commit);
+	unuse_commit_buffer(commit, msg);
 }
 
 static void update_index_from_diff(struct diff_queue_struct *q,
diff --git a/builtin/rev-list.c b/builtin/rev-list.c
index 9f9290537..ff84a825f 100644
--- a/builtin/rev-list.c
+++ b/builtin/rev-list.c
@@ -106,7 +106,7 @@ static void show_commit(struct commit *commit, void *data)
 	else
 		putchar('\n');
 
-	if (revs->verbose_header && commit->buffer) {
+	if (revs->verbose_header && get_cached_commit_buffer(commit, NULL)) {
 		struct strbuf buf = STRBUF_INIT;
 		struct pretty_print_context ctx = {0};
 		ctx.abbrev = revs->abbrev;
@@ -173,8 +173,7 @@ static void finish_commit(struct commit *commit, void *data)
 		free_commit_list(commit->parents);
 		commit->parents = NULL;
 	}
-	free(commit->buffer);
-	commit->buffer = NULL;
+	free_commit_buffer(commit);
 }
 
 static void finish_object(struct object *obj,