Merge branch 'rs/strbuf-expand-step'

Code clean-up around strbuf_expand() API.

* rs/strbuf-expand-step:
  strbuf: simplify strbuf_expand_literal_cb()
  replace strbuf_expand() with strbuf_expand_step()
  replace strbuf_expand_dict_cb() with strbuf_expand_step()
  strbuf: factor out strbuf_expand_step()
  pretty: factor out expand_separator()

builtin/branch.c

@@ -366,17 +366,8 @@ static const char *quote_literal_for_format(const char *s)
 	static struct strbuf buf = STRBUF_INIT;
 
 	strbuf_reset(&buf);
-	while (*s) {
+	while (strbuf_expand_step(&buf, &s))
-		const char *ep = strchrnul(s, '%');
+		strbuf_addstr(&buf, "%%");
-		if (s < ep)
-			strbuf_add(&buf, s, ep - s);
-		if (*ep == '%') {
-			strbuf_addstr(&buf, "%%");
-			s = ep + 1;
-		} else {
-			s = ep;
-		}
-	}
 	return buf.buf;
 }
 

builtin/cat-file.c

@@ -309,10 +309,8 @@ static int is_atom(const char *atom, const char *s, int slen)
 }
 
 static void expand_atom(struct strbuf *sb, const char *atom, int len,
-			void *vdata)
+			struct expand_data *data)
 {
-	struct expand_data *data = vdata;
-
 	if (is_atom("objectname", atom, len)) {
 		if (!data->mark_query)
 			strbuf_addstr(sb, oid_to_hex(&data->oid));
@@ -346,19 +344,21 @@ static void expand_atom(struct strbuf *sb, const char *atom, int len,
 		die("unknown format element: %.*s", len, atom);
 }
 
-static size_t expand_format(struct strbuf *sb, const char *start, void *data)
+static void expand_format(struct strbuf *sb, const char *start,
+			  struct expand_data *data)
 {
-	const char *end;
+	while (strbuf_expand_step(sb, &start)) {
+		const char *end;
 
-	if (*start != '(')
+		if (skip_prefix(start, "%", &start) || *start != '(')
-		return 0;
+			strbuf_addch(sb, '%');
-	end = strchr(start + 1, ')');
+		else if (!(end = strchr(start + 1, ')')))
-	if (!end)
+			die("format element '%s' does not end in ')'", start);
-		die("format element '%s' does not end in ')'", start);
+		else {
-
+			expand_atom(sb, start + 1, end - start - 1, data);
-	expand_atom(sb, start + 1, end - start - 1, data);
+			start = end + 1;
-
+		}
-	return end - start + 1;
+	}
 }
 
 static void batch_write(struct batch_options *opt, const void *data, int len)
@@ -495,7 +495,7 @@ static void batch_object_write(const char *obj_name,
 	if (!opt->format) {
 		print_default_format(scratch, data, opt);
 	} else {
-		strbuf_expand(scratch, opt->format, expand_format, data);
+		expand_format(scratch, opt->format, data);
 		strbuf_addch(scratch, opt->output_delim);
 	}
 
@@ -773,9 +773,8 @@ static int batch_objects(struct batch_options *opt)
 	 */
 	memset(&data, 0, sizeof(data));
 	data.mark_query = 1;
-	strbuf_expand(&output,
+	expand_format(&output,
 		      opt->format ? opt->format : DEFAULT_FORMAT,
-		      expand_format,
 		      &data);
 	data.mark_query = 0;
 	strbuf_release(&output);

builtin/ls-files.c

@@ -264,74 +264,57 @@ static void expand_objectsize(struct strbuf *line, const struct object_id *oid,
 		strbuf_addstr(line, "-");
 	}
 }
-struct show_index_data {
-	const char *pathname;
-	struct index_state *istate;
-	const struct cache_entry *ce;
-};
-
-static size_t expand_show_index(struct strbuf *sb, const char *start,
-				void *context)
-{
-	struct show_index_data *data = context;
-	const char *end;
-	const char *p;
-	size_t len = strbuf_expand_literal_cb(sb, start, NULL);
-	struct stat st;
-
-	if (len)
-		return len;
-	if (*start != '(')
-		die(_("bad ls-files format: element '%s' "
-		      "does not start with '('"), start);
-
-	end = strchr(start + 1, ')');
-	if (!end)
-		die(_("bad ls-files format: element '%s' "
-		      "does not end in ')'"), start);
-
-	len = end - start + 1;
-	if (skip_prefix(start, "(objectmode)", &p))
-		strbuf_addf(sb, "%06o", data->ce->ce_mode);
-	else if (skip_prefix(start, "(objectname)", &p))
-		strbuf_add_unique_abbrev(sb, &data->ce->oid, abbrev);
-	else if (skip_prefix(start, "(objecttype)", &p))
-		strbuf_addstr(sb, type_name(object_type(data->ce->ce_mode)));
-	else if (skip_prefix(start, "(objectsize:padded)", &p))
-		expand_objectsize(sb, &data->ce->oid, object_type(data->ce->ce_mode), 1);
-	else if (skip_prefix(start, "(objectsize)", &p))
-		expand_objectsize(sb, &data->ce->oid, object_type(data->ce->ce_mode), 0);
-	else if (skip_prefix(start, "(stage)", &p))
-		strbuf_addf(sb, "%d", ce_stage(data->ce));
-	else if (skip_prefix(start, "(eolinfo:index)", &p))
-		strbuf_addstr(sb, S_ISREG(data->ce->ce_mode) ?
-			      get_cached_convert_stats_ascii(data->istate,
-			      data->ce->name) : "");
-	else if (skip_prefix(start, "(eolinfo:worktree)", &p))
-		strbuf_addstr(sb, !lstat(data->pathname, &st) &&
-			      S_ISREG(st.st_mode) ?
-			      get_wt_convert_stats_ascii(data->pathname) : "");
-	else if (skip_prefix(start, "(eolattr)", &p))
-		strbuf_addstr(sb, get_convert_attr_ascii(data->istate,
-			      data->pathname));
-	else if (skip_prefix(start, "(path)", &p))
-		write_name_to_buf(sb, data->pathname);
-	else
-		die(_("bad ls-files format: %%%.*s"), (int)len, start);
-
-	return len;
-}
 
 static void show_ce_fmt(struct repository *repo, const struct cache_entry *ce,
 			const char *format, const char *fullname) {
-	struct show_index_data data = {
-		.pathname = fullname,
-		.istate = repo->index,
-		.ce = ce,
-	};
 	struct strbuf sb = STRBUF_INIT;
 
-	strbuf_expand(&sb, format, expand_show_index, &data);
+	while (strbuf_expand_step(&sb, &format)) {
+		const char *end;
+		size_t len;
+		struct stat st;
+
+		if (skip_prefix(format, "%", &format))
+			strbuf_addch(&sb, '%');
+		else if ((len = strbuf_expand_literal(&sb, format)))
+			format += len;
+		else if (*format != '(')
+			die(_("bad ls-files format: element '%s' "
+			      "does not start with '('"), format);
+		else if (!(end = strchr(format + 1, ')')))
+			die(_("bad ls-files format: element '%s' "
+			      "does not end in ')'"), format);
+		else if (skip_prefix(format, "(objectmode)", &format))
+			strbuf_addf(&sb, "%06o", ce->ce_mode);
+		else if (skip_prefix(format, "(objectname)", &format))
+			strbuf_add_unique_abbrev(&sb, &ce->oid, abbrev);
+		else if (skip_prefix(format, "(objecttype)", &format))
+			strbuf_addstr(&sb, type_name(object_type(ce->ce_mode)));
+		else if (skip_prefix(format, "(objectsize:padded)", &format))
+			expand_objectsize(&sb, &ce->oid,
+					  object_type(ce->ce_mode), 1);
+		else if (skip_prefix(format, "(objectsize)", &format))
+			expand_objectsize(&sb, &ce->oid,
+					  object_type(ce->ce_mode), 0);
+		else if (skip_prefix(format, "(stage)", &format))
+			strbuf_addf(&sb, "%d", ce_stage(ce));
+		else if (skip_prefix(format, "(eolinfo:index)", &format))
+			strbuf_addstr(&sb, S_ISREG(ce->ce_mode) ?
+				      get_cached_convert_stats_ascii(repo->index,
+				      ce->name) : "");
+		else if (skip_prefix(format, "(eolinfo:worktree)", &format))
+			strbuf_addstr(&sb, !lstat(fullname, &st) &&
+				      S_ISREG(st.st_mode) ?
+				      get_wt_convert_stats_ascii(fullname) : "");
+		else if (skip_prefix(format, "(eolattr)", &format))
+			strbuf_addstr(&sb, get_convert_attr_ascii(repo->index,
+								 fullname));
+		else if (skip_prefix(format, "(path)", &format))
+			write_name_to_buf(&sb, fullname);
+		else
+			die(_("bad ls-files format: %%%.*s"),
+			    (int)(end - format + 1), format);
+	}
 	strbuf_addch(&sb, line_terminator);
 	fwrite(sb.buf, sb.len, 1, stdout);
 	strbuf_release(&sb);

builtin/ls-tree.c

@@ -55,63 +55,6 @@ struct ls_tree_options {
 	const char *format;
 };
 
-struct show_tree_data {
-	struct ls_tree_options *options;
-	unsigned mode;
-	enum object_type type;
-	const struct object_id *oid;
-	const char *pathname;
-	struct strbuf *base;
-};
-
-static size_t expand_show_tree(struct strbuf *sb, const char *start,
-			       void *context)
-{
-	struct show_tree_data *data = context;
-	struct ls_tree_options *options = data->options;
-	const char *end;
-	const char *p;
-	unsigned int errlen;
-	size_t len = strbuf_expand_literal_cb(sb, start, NULL);
-
-	if (len)
-		return len;
-	if (*start != '(')
-		die(_("bad ls-tree format: element '%s' does not start with '('"), start);
-
-	end = strchr(start + 1, ')');
-	if (!end)
-		die(_("bad ls-tree format: element '%s' does not end in ')'"), start);
-
-	len = end - start + 1;
-	if (skip_prefix(start, "(objectmode)", &p)) {
-		strbuf_addf(sb, "%06o", data->mode);
-	} else if (skip_prefix(start, "(objecttype)", &p)) {
-		strbuf_addstr(sb, type_name(data->type));
-	} else if (skip_prefix(start, "(objectsize:padded)", &p)) {
-		expand_objectsize(sb, data->oid, data->type, 1);
-	} else if (skip_prefix(start, "(objectsize)", &p)) {
-		expand_objectsize(sb, data->oid, data->type, 0);
-	} else if (skip_prefix(start, "(objectname)", &p)) {
-		strbuf_add_unique_abbrev(sb, data->oid, options->abbrev);
-	} else if (skip_prefix(start, "(path)", &p)) {
-		const char *name = data->base->buf;
-		const char *prefix = options->chomp_prefix ? options->ls_tree_prefix : NULL;
-		struct strbuf sbuf = STRBUF_INIT;
-		size_t baselen = data->base->len;
-
-		strbuf_addstr(data->base, data->pathname);
-		name = relative_path(data->base->buf, prefix, &sbuf);
-		quote_c_style(name, sb, NULL, 0);
-		strbuf_setlen(data->base, baselen);
-		strbuf_release(&sbuf);
-	} else {
-		errlen = (unsigned long)len;
-		die(_("bad ls-tree format: %%%.*s"), errlen, start);
-	}
-	return len;
-}
-
 static int show_recursive(struct ls_tree_options *options, const char *base,
 			  size_t baselen, const char *pathname)
 {
@@ -150,14 +93,7 @@ static int show_tree_fmt(const struct object_id *oid, struct strbuf *base,
 	int recurse = 0;
 	struct strbuf sb = STRBUF_INIT;
 	enum object_type type = object_type(mode);
-	struct show_tree_data cb_data = {
+	const char *format = options->format;
-		.options = options,
-		.mode = mode,
-		.type = type,
-		.oid = oid,
-		.pathname = pathname,
-		.base = base,
-	};
 
 	if (type == OBJ_TREE && show_recursive(options, base->buf, base->len, pathname))
 		recurse = READ_TREE_RECURSIVE;
@@ -166,7 +102,46 @@ static int show_tree_fmt(const struct object_id *oid, struct strbuf *base,
 	if (type == OBJ_BLOB && (options->ls_options & LS_TREE_ONLY))
 		return 0;
 
-	strbuf_expand(&sb, options->format, expand_show_tree, &cb_data);
+	while (strbuf_expand_step(&sb, &format)) {
+		const char *end;
+		size_t len;
+
+		if (skip_prefix(format, "%", &format))
+			strbuf_addch(&sb, '%');
+		else if ((len = strbuf_expand_literal(&sb, format)))
+			format += len;
+		else if (*format != '(')
+			die(_("bad ls-tree format: element '%s' "
+			      "does not start with '('"), format);
+		else if (!(end = strchr(format + 1, ')')))
+			die(_("bad ls-tree format: element '%s' "
+			      "does not end in ')'"), format);
+		else if (skip_prefix(format, "(objectmode)", &format))
+			strbuf_addf(&sb, "%06o", mode);
+		else if (skip_prefix(format, "(objecttype)", &format))
+			strbuf_addstr(&sb, type_name(type));
+		else if (skip_prefix(format, "(objectsize:padded)", &format))
+			expand_objectsize(&sb, oid, type, 1);
+		else if (skip_prefix(format, "(objectsize)", &format))
+			expand_objectsize(&sb, oid, type, 0);
+		else if (skip_prefix(format, "(objectname)", &format))
+			strbuf_add_unique_abbrev(&sb, oid, options->abbrev);
+		else if (skip_prefix(format, "(path)", &format)) {
+			const char *name;
+			const char *prefix = options->chomp_prefix ?
+					     options->ls_tree_prefix : NULL;
+			struct strbuf sbuf = STRBUF_INIT;
+			size_t baselen = base->len;
+
+			strbuf_addstr(base, pathname);
+			name = relative_path(base->buf, prefix, &sbuf);
+			quote_c_style(name, &sb, NULL, 0);
+			strbuf_setlen(base, baselen);
+			strbuf_release(&sbuf);
+		} else
+			die(_("bad ls-tree format: %%%.*s"),
+			    (int)(end - format + 1), format);
+	}
 	strbuf_addch(&sb, options->null_termination ? '\0' : '\n');
 	fwrite(sb.buf, sb.len, 1, stdout);
 	strbuf_release(&sb);

convert.c

@@ -634,23 +634,21 @@ static int filter_buffer_or_fd(int in UNUSED, int out, void *data)
 	 */
 	struct child_process child_process = CHILD_PROCESS_INIT;
 	struct filter_params *params = (struct filter_params *)data;
+	const char *format = params->cmd;
 	int write_err, status;
 
 	/* apply % substitution to cmd */
 	struct strbuf cmd = STRBUF_INIT;
-	struct strbuf path = STRBUF_INIT;
-	struct strbuf_expand_dict_entry dict[] = {
-		{ "f", NULL, },
-		{ NULL, NULL, },
-	};
 
-	/* quote the path to preserve spaces, etc. */
+	/* expand all %f with the quoted path; quote to preserve space, etc. */
-	sq_quote_buf(&path, params->path);
+	while (strbuf_expand_step(&cmd, &format)) {
-	dict[0].value = path.buf;
+		if (skip_prefix(format, "%", &format))
-
+			strbuf_addch(&cmd, '%');
-	/* expand all %f with the quoted path */
+		else if (skip_prefix(format, "f", &format))
-	strbuf_expand(&cmd, params->cmd, strbuf_expand_dict_cb, &dict);
+			sq_quote_buf(&cmd, params->path);
-	strbuf_release(&path);
+		else
+			strbuf_addch(&cmd, '%');
+	}
 
 	strvec_push(&child_process.args, cmd.buf);
 	child_process.use_shell = 1;

daemon.c

@@ -144,42 +144,6 @@ static void NORETURN daemon_die(const char *err, va_list params)
 	exit(1);
 }
 
-struct expand_path_context {
-	const char *directory;
-	struct hostinfo *hostinfo;
-};
-
-static size_t expand_path(struct strbuf *sb, const char *placeholder, void *ctx)
-{
-	struct expand_path_context *context = ctx;
-	struct hostinfo *hi = context->hostinfo;
-
-	switch (placeholder[0]) {
-	case 'H':
-		strbuf_addbuf(sb, &hi->hostname);
-		return 1;
-	case 'C':
-		if (placeholder[1] == 'H') {
-			strbuf_addstr(sb, get_canon_hostname(hi));
-			return 2;
-		}
-		break;
-	case 'I':
-		if (placeholder[1] == 'P') {
-			strbuf_addstr(sb, get_ip_address(hi));
-			return 2;
-		}
-		break;
-	case 'P':
-		strbuf_addbuf(sb, &hi->tcp_port);
-		return 1;
-	case 'D':
-		strbuf_addstr(sb, context->directory);
-		return 1;
-	}
-	return 0;
-}
-
 static const char *path_ok(const char *directory, struct hostinfo *hi)
 {
 	static char rpath[PATH_MAX];
@@ -223,10 +187,7 @@ static const char *path_ok(const char *directory, struct hostinfo *hi)
 	}
 	else if (interpolated_path && hi->saw_extended_args) {
 		struct strbuf expanded_path = STRBUF_INIT;
-		struct expand_path_context context;
+		const char *format = interpolated_path;
-
-		context.directory = directory;
-		context.hostinfo = hi;
 
 		if (*dir != '/') {
 			/* Allow only absolute */
@@ -234,8 +195,24 @@ static const char *path_ok(const char *directory, struct hostinfo *hi)
 			return NULL;
 		}
 
-		strbuf_expand(&expanded_path, interpolated_path,
+		while (strbuf_expand_step(&expanded_path, &format)) {
-			      expand_path, &context);
+			if (skip_prefix(format, "%", &format))
+				strbuf_addch(&expanded_path, '%');
+			else if (skip_prefix(format, "H", &format))
+				strbuf_addbuf(&expanded_path, &hi->hostname);
+			else if (skip_prefix(format, "CH", &format))
+				strbuf_addstr(&expanded_path,
+					      get_canon_hostname(hi));
+			else if (skip_prefix(format, "IP", &format))
+				strbuf_addstr(&expanded_path,
+					      get_ip_address(hi));
+			else if (skip_prefix(format, "P", &format))
+				strbuf_addbuf(&expanded_path, &hi->tcp_port);
+			else if (skip_prefix(format, "D", &format))
+				strbuf_addstr(&expanded_path, directory);
+			else
+				strbuf_addch(&expanded_path, '%');
+		}
 
 		rlen = strlcpy(interp_path, expanded_path.buf,
 			       sizeof(interp_path));

merge-ll.c

@@ -192,24 +192,15 @@ static enum ll_merge_result ll_ext_merge(const struct ll_merge_driver *fn,
 			const struct ll_merge_options *opts,
 			int marker_size)
 {
-	char temp[4][50];
+	char temp[3][50];
 	struct strbuf cmd = STRBUF_INIT;
-	struct strbuf_expand_dict_entry dict[6];
+	const char *format = fn->cmdline;
-	struct strbuf path_sq = STRBUF_INIT;
 	struct child_process child = CHILD_PROCESS_INIT;
 	int status, fd, i;
 	struct stat st;
 	enum ll_merge_result ret;
 	assert(opts);
 
-	sq_quote_buf(&path_sq, path);
-	dict[0].placeholder = "O"; dict[0].value = temp[0];
-	dict[1].placeholder = "A"; dict[1].value = temp[1];
-	dict[2].placeholder = "B"; dict[2].value = temp[2];
-	dict[3].placeholder = "L"; dict[3].value = temp[3];
-	dict[4].placeholder = "P"; dict[4].value = path_sq.buf;
-	dict[5].placeholder = NULL; dict[5].value = NULL;
-
 	if (!fn->cmdline)
 		die("custom merge driver %s lacks command line.", fn->name);
 
@@ -218,9 +209,23 @@ static enum ll_merge_result ll_ext_merge(const struct ll_merge_driver *fn,
 	create_temp(orig, temp[0], sizeof(temp[0]));
 	create_temp(src1, temp[1], sizeof(temp[1]));
 	create_temp(src2, temp[2], sizeof(temp[2]));
-	xsnprintf(temp[3], sizeof(temp[3]), "%d", marker_size);
 
-	strbuf_expand(&cmd, fn->cmdline, strbuf_expand_dict_cb, &dict);
+	while (strbuf_expand_step(&cmd, &format)) {
+		if (skip_prefix(format, "%", &format))
+			strbuf_addch(&cmd, '%');
+		else if (skip_prefix(format, "O", &format))
+			strbuf_addstr(&cmd, temp[0]);
+		else if (skip_prefix(format, "A", &format))
+			strbuf_addstr(&cmd, temp[1]);
+		else if (skip_prefix(format, "B", &format))
+			strbuf_addstr(&cmd, temp[2]);
+		else if (skip_prefix(format, "L", &format))
+			strbuf_addf(&cmd, "%d", marker_size);
+		else if (skip_prefix(format, "P", &format))
+			sq_quote_buf(&cmd, path);
+		else
+			strbuf_addch(&cmd, '%');
+	}
 
 	child.use_shell = 1;
 	strvec_push(&child.args, cmd.buf);
@@ -242,8 +247,6 @@ static enum ll_merge_result ll_ext_merge(const struct ll_merge_driver *fn,
 	for (i = 0; i < 3; i++)
 		unlink_or_warn(temp[i]);
 	strbuf_release(&cmd);
-	strbuf_release(&path_sq);
-
 	if (!status)
 		ret = LL_MERGE_OK;
 	else if (status <= 128)

pretty.c

@@ -1251,6 +1251,27 @@ static int format_trailer_match_cb(const struct strbuf *key, void *ud)
 	return 0;
 }
 
+static struct strbuf *expand_separator(struct strbuf *sb,
+				       const char *argval, size_t arglen)
+{
+	char *fmt = xstrndup(argval, arglen);
+	const char *format = fmt;
+
+	strbuf_reset(sb);
+	while (strbuf_expand_step(sb, &format)) {
+		size_t len;
+
+		if (skip_prefix(format, "%", &format))
+			strbuf_addch(sb, '%');
+		else if ((len = strbuf_expand_literal(sb, format)))
+			format += len;
+		else
+			strbuf_addch(sb, '%');
+	}
+	free(fmt);
+	return sb;
+}
+
 int format_set_trailers_options(struct process_trailer_options *opts,
 				struct string_list *filter_list,
 				struct strbuf *sepbuf,
@@ -1279,21 +1300,9 @@ int format_set_trailers_options(struct process_trailer_options *opts,
 			opts->filter_data = filter_list;
 			opts->only_trailers = 1;
 		} else if (match_placeholder_arg_value(*arg, "separator", arg, &argval, &arglen)) {
-			char *fmt;
+			opts->separator = expand_separator(sepbuf, argval, arglen);
-
-			strbuf_reset(sepbuf);
-			fmt = xstrndup(argval, arglen);
-			strbuf_expand(sepbuf, fmt, strbuf_expand_literal_cb, NULL);
-			free(fmt);
-			opts->separator = sepbuf;
 		} else if (match_placeholder_arg_value(*arg, "key_value_separator", arg, &argval, &arglen)) {
-			char *fmt;
+			opts->key_value_separator = expand_separator(kvsepbuf, argval, arglen);
-
-			strbuf_reset(kvsepbuf);
-			fmt = xstrndup(argval, arglen);
-			strbuf_expand(kvsepbuf, fmt, strbuf_expand_literal_cb, NULL);
-			free(fmt);
-			opts->key_value_separator = kvsepbuf;
 		} else if (!match_placeholder_bool_arg(*arg, "only", arg, &opts->only_trailers) &&
 			   !match_placeholder_bool_arg(*arg, "unfold", arg, &opts->unfold) &&
 			   !match_placeholder_bool_arg(*arg, "keyonly", arg, &opts->key_only) &&
@@ -1387,7 +1396,7 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 	char **slot;
 
 	/* these are independent of the commit */
-	res = strbuf_expand_literal_cb(sb, placeholder, NULL);
+	res = strbuf_expand_literal(sb, placeholder);
 	if (res)
 		return res;
 
@@ -1805,7 +1814,7 @@ static size_t format_and_pad_commit(struct strbuf *sb, /* in UTF-8 */
 
 static size_t format_commit_item(struct strbuf *sb, /* in UTF-8 */
 				 const char *placeholder,
-				 void *context)
+				 struct format_commit_context *context)
 {
 	size_t consumed, orig_len;
 	enum {
@@ -1844,7 +1853,7 @@ static size_t format_commit_item(struct strbuf *sb, /* in UTF-8 */
 	}
 
 	orig_len = sb->len;
-	if (((struct format_commit_context *)context)->flush_type != no_flush)
+	if ((context)->flush_type != no_flush)
 		consumed = format_and_pad_commit(sb, placeholder, context);
 	else
 		consumed = format_commit_one(sb, placeholder, context);
@@ -1863,30 +1872,6 @@ static size_t format_commit_item(struct strbuf *sb, /* in UTF-8 */
 	return consumed + 1;
 }
 
-static size_t userformat_want_item(struct strbuf *sb UNUSED,
-				   const char *placeholder,
-				   void *context)
-{
-	struct userformat_want *w = context;
-
-	if (*placeholder == '+' || *placeholder == '-' || *placeholder == ' ')
-		placeholder++;
-
-	switch (*placeholder) {
-	case 'N':
-		w->notes = 1;
-		break;
-	case 'S':
-		w->source = 1;
-		break;
-	case 'd':
-	case 'D':
-		w->decorate = 1;
-		break;
-	}
-	return 0;
-}
-
 void userformat_find_requirements(const char *fmt, struct userformat_want *w)
 {
 	struct strbuf dummy = STRBUF_INIT;
@@ -1896,7 +1881,26 @@ void userformat_find_requirements(const char *fmt, struct userformat_want *w)
 			return;
 		fmt = user_format;
 	}
-	strbuf_expand(&dummy, fmt, userformat_want_item, w);
+	while (strbuf_expand_step(&dummy, &fmt)) {
+		if (skip_prefix(fmt, "%", &fmt))
+			continue;
+
+		if (*fmt == '+' || *fmt == '-' || *fmt == ' ')
+			fmt++;
+
+		switch (*fmt) {
+		case 'N':
+			w->notes = 1;
+			break;
+		case 'S':
+			w->source = 1;
+			break;
+		case 'd':
+		case 'D':
+			w->decorate = 1;
+			break;
+		}
+	}
 	strbuf_release(&dummy);
 }
 
@@ -1914,7 +1918,16 @@ void repo_format_commit_message(struct repository *r,
 	const char *output_enc = pretty_ctx->output_encoding;
 	const char *utf8 = "UTF-8";
 
-	strbuf_expand(sb, format, format_commit_item, &context);
+	while (strbuf_expand_step(sb, &format)) {
+		size_t len;
+
+		if (skip_prefix(format, "%", &format))
+			strbuf_addch(sb, '%');
+		else if ((len = format_commit_item(sb, format, &context)))
+			format += len;
+		else
+			strbuf_addch(sb, '%');
+	}
 	rewrap_message_tail(sb, &context, 0, 0, 0);
 
 	/*

strbuf.c

@@ -416,36 +416,19 @@ void strbuf_vaddf(struct strbuf *sb, const char *fmt, va_list ap)
 	strbuf_setlen(sb, sb->len + len);
 }
 
-void strbuf_expand(struct strbuf *sb, const char *format, expand_fn_t fn,
+int strbuf_expand_step(struct strbuf *sb, const char **formatp)
-		   void *context)
 {
-	for (;;) {
+	const char *format = *formatp;
-		const char *percent;
+	const char *percent = strchrnul(format, '%');
-		size_t consumed;
 
-		percent = strchrnul(format, '%');
+	strbuf_add(sb, format, percent - format);
-		strbuf_add(sb, format, percent - format);
+	if (!*percent)
-		if (!*percent)
+		return 0;
-			break;
+	*formatp = percent + 1;
-		format = percent + 1;
+	return 1;
-
-		if (*format == '%') {
-			strbuf_addch(sb, '%');
-			format++;
-			continue;
-		}
-
-		consumed = fn(sb, format, context);
-		if (consumed)
-			format += consumed;
-		else
-			strbuf_addch(sb, '%');
-	}
 }
 
-size_t strbuf_expand_literal_cb(struct strbuf *sb,
+size_t strbuf_expand_literal(struct strbuf *sb, const char *placeholder)
-				const char *placeholder,
-				void *context UNUSED)
 {
 	int ch;
 
@@ -464,22 +447,6 @@ size_t strbuf_expand_literal_cb(struct strbuf *sb,
 	return 0;
 }
 
-size_t strbuf_expand_dict_cb(struct strbuf *sb, const char *placeholder,
-		void *context)
-{
-	struct strbuf_expand_dict_entry *e = context;
-	size_t len;
-
-	for (; e->placeholder && (len = strlen(e->placeholder)); e++) {
-		if (!strncmp(placeholder, e->placeholder, len)) {
-			if (e->value)
-				strbuf_addstr(sb, e->value);
-			return len;
-		}
-	}
-	return 0;
-}
-
 void strbuf_addbuf_percentquote(struct strbuf *dst, const struct strbuf *src)
 {
 	size_t i, len = src->len;
@@ -1028,12 +995,7 @@ void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm *tm,
 	 * we want for %z, but the computation for %s has to convert to number
 	 * of seconds.
 	 */
-	for (;;) {
+	while (strbuf_expand_step(&munged_fmt, &fmt)) {
-		const char *percent = strchrnul(fmt, '%');
-		strbuf_add(&munged_fmt, fmt, percent - fmt);
-		if (!*percent)
-			break;
-		fmt = percent + 1;
 		switch (*fmt) {
 		case '%':
 			strbuf_addstr(&munged_fmt, "%%");

strbuf.h

@@ -314,58 +314,19 @@ const char *strbuf_join_argv(struct strbuf *buf, int argc,
 			     const char **argv, char delim);
 
 /**
- * This function can be used to expand a format string containing
+ * Used with `strbuf_expand_step` to expand the literals %n and %x
- * placeholders. To that end, it parses the string and calls the specified
+ * followed by two hexadecimal digits. Returns the number of recognized
- * function for every percent sign found.
+ * characters.
- *
- * The callback function is given a pointer to the character after the `%`
- * and a pointer to the struct strbuf.  It is expected to add the expanded
- * version of the placeholder to the strbuf, e.g. to add a newline
- * character if the letter `n` appears after a `%`.  The function returns
- * the length of the placeholder recognized and `strbuf_expand()` skips
- * over it.
- *
- * The format `%%` is automatically expanded to a single `%` as a quoting
- * mechanism; callers do not need to handle the `%` placeholder themselves,
- * and the callback function will not be invoked for this placeholder.
- *
- * All other characters (non-percent and not skipped ones) are copied
- * verbatim to the strbuf.  If the callback returned zero, meaning that the
- * placeholder is unknown, then the percent sign is copied, too.
- *
- * In order to facilitate caching and to make it possible to give
- * parameters to the callback, `strbuf_expand()` passes a context
- * pointer with any kind of data.
  */
-typedef size_t (*expand_fn_t) (struct strbuf *sb,
+size_t strbuf_expand_literal(struct strbuf *sb, const char *placeholder);
-			       const char *placeholder,
-			       void *context);
-void strbuf_expand(struct strbuf *sb,
-		   const char *format,
-		   expand_fn_t fn,
-		   void *context);
 
 /**
- * Used as callback for `strbuf_expand` to only expand literals
+ * If the string pointed to by `formatp` contains a percent sign ("%"),
- * (i.e. %n and %xNN). The context argument is ignored.
+ * advance it to point to the character following the next one and
+ * return 1, otherwise return 0.  Append the substring before that
+ * percent sign to `sb`, or the whole string if there is none.
  */
-size_t strbuf_expand_literal_cb(struct strbuf *sb,
+int strbuf_expand_step(struct strbuf *sb, const char **formatp);
-				const char *placeholder,
-				void *context);
-
-/**
- * Used as callback for `strbuf_expand()`, expects an array of
- * struct strbuf_expand_dict_entry as context, i.e. pairs of
- * placeholder and replacement string.  The array needs to be
- * terminated by an entry with placeholder set to NULL.
- */
-struct strbuf_expand_dict_entry {
-	const char *placeholder;
-	const char *value;
-};
-size_t strbuf_expand_dict_cb(struct strbuf *sb,
-			     const char *placeholder,
-			     void *context);
 
 /**
  * Append the contents of one strbuf to another, quoting any