Squashed 'third_party/git/' content from commit cb71568594

git-subtree-dir: third_party/git
git-subtree-split: cb715685942260375e1eb8153b0768a376e4ece7

1 files changed, 1187 insertions, 0 deletions

diff --git a/trailer.c b/trailer.c
new file mode 100644
index 000000000000..0c414f2fed2b
--- /dev/null
+++ b/trailer.c
@@ -0,0 +1,1187 @@
+#include "cache.h"
+#include "config.h"
+#include "string-list.h"
+#include "run-command.h"
+#include "commit.h"
+#include "tempfile.h"
+#include "trailer.h"
+#include "list.h"
+/*
+ * Copyright (c) 2013, 2014 Christian Couder <chriscool@tuxfamily.org>
+ */
+
+struct conf_info {
+	char *name;
+	char *key;
+	char *command;
+	enum trailer_where where;
+	enum trailer_if_exists if_exists;
+	enum trailer_if_missing if_missing;
+};
+
+static struct conf_info default_conf_info;
+
+struct trailer_item {
+	struct list_head list;
+	/*
+	 * If this is not a trailer line, the line is stored in value
+	 * (excluding the terminating newline) and token is NULL.
+	 */
+	char *token;
+	char *value;
+};
+
+struct arg_item {
+	struct list_head list;
+	char *token;
+	char *value;
+	struct conf_info conf;
+};
+
+static LIST_HEAD(conf_head);
+
+static char *separators = ":";
+
+static int configured;
+
+#define TRAILER_ARG_STRING "$ARG"
+
+static const char *git_generated_prefixes[] = {
+	"Signed-off-by: ",
+	"(cherry picked from commit ",
+	NULL
+};
+
+/* Iterate over the elements of the list. */
+#define list_for_each_dir(pos, head, is_reverse) \
+	for (pos = is_reverse ? (head)->prev : (head)->next; \
+		pos != (head); \
+		pos = is_reverse ? pos->prev : pos->next)
+
+static int after_or_end(enum trailer_where where)
+{
+	return (where == WHERE_AFTER) || (where == WHERE_END);
+}
+
+/*
+ * Return the length of the string not including any final
+ * punctuation. E.g., the input "Signed-off-by:" would return
+ * 13, stripping the trailing punctuation but retaining
+ * internal punctuation.
+ */
+static size_t token_len_without_separator(const char *token, size_t len)
+{
+	while (len > 0 && !isalnum(token[len - 1]))
+		len--;
+	return len;
+}
+
+static int same_token(struct trailer_item *a, struct arg_item *b)
+{
+	size_t a_len, b_len, min_len;
+
+	if (!a->token)
+		return 0;
+
+	a_len = token_len_without_separator(a->token, strlen(a->token));
+	b_len = token_len_without_separator(b->token, strlen(b->token));
+	min_len = (a_len > b_len) ? b_len : a_len;
+
+	return !strncasecmp(a->token, b->token, min_len);
+}
+
+static int same_value(struct trailer_item *a, struct arg_item *b)
+{
+	return !strcasecmp(a->value, b->value);
+}
+
+static int same_trailer(struct trailer_item *a, struct arg_item *b)
+{
+	return same_token(a, b) && same_value(a, b);
+}
+
+static inline int is_blank_line(const char *str)
+{
+	const char *s = str;
+	while (*s && *s != '\n' && isspace(*s))
+		s++;
+	return !*s || *s == '\n';
+}
+
+static inline void strbuf_replace(struct strbuf *sb, const char *a, const char *b)
+{
+	const char *ptr = strstr(sb->buf, a);
+	if (ptr)
+		strbuf_splice(sb, ptr - sb->buf, strlen(a), b, strlen(b));
+}
+
+static void free_trailer_item(struct trailer_item *item)
+{
+	free(item->token);
+	free(item->value);
+	free(item);
+}
+
+static void free_arg_item(struct arg_item *item)
+{
+	free(item->conf.name);
+	free(item->conf.key);
+	free(item->conf.command);
+	free(item->token);
+	free(item->value);
+	free(item);
+}
+
+static char last_non_space_char(const char *s)
+{
+	int i;
+	for (i = strlen(s) - 1; i >= 0; i--)
+		if (!isspace(s[i]))
+			return s[i];
+	return '\0';
+}
+
+static void print_tok_val(FILE *outfile, const char *tok, const char *val)
+{
+	char c;
+
+	if (!tok) {
+		fprintf(outfile, "%s\n", val);
+		return;
+	}
+
+	c = last_non_space_char(tok);
+	if (!c)
+		return;
+	if (strchr(separators, c))
+		fprintf(outfile, "%s%s\n", tok, val);
+	else
+		fprintf(outfile, "%s%c %s\n", tok, separators[0], val);
+}
+
+static void print_all(FILE *outfile, struct list_head *head,
+		      const struct process_trailer_options *opts)
+{
+	struct list_head *pos;
+	struct trailer_item *item;
+	list_for_each(pos, head) {
+		item = list_entry(pos, struct trailer_item, list);
+		if ((!opts->trim_empty || strlen(item->value) > 0) &&
+		    (!opts->only_trailers || item->token))
+			print_tok_val(outfile, item->token, item->value);
+	}
+}
+
+static struct trailer_item *trailer_from_arg(struct arg_item *arg_tok)
+{
+	struct trailer_item *new_item = xcalloc(sizeof(*new_item), 1);
+	new_item->token = arg_tok->token;
+	new_item->value = arg_tok->value;
+	arg_tok->token = arg_tok->value = NULL;
+	free_arg_item(arg_tok);
+	return new_item;
+}
+
+static void add_arg_to_input_list(struct trailer_item *on_tok,
+				  struct arg_item *arg_tok)
+{
+	int aoe = after_or_end(arg_tok->conf.where);
+	struct trailer_item *to_add = trailer_from_arg(arg_tok);
+	if (aoe)
+		list_add(&to_add->list, &on_tok->list);
+	else
+		list_add_tail(&to_add->list, &on_tok->list);
+}
+
+static int check_if_different(struct trailer_item *in_tok,
+			      struct arg_item *arg_tok,
+			      int check_all,
+			      struct list_head *head)
+{
+	enum trailer_where where = arg_tok->conf.where;
+	struct list_head *next_head;
+	do {
+		if (same_trailer(in_tok, arg_tok))
+			return 0;
+		/*
+		 * if we want to add a trailer after another one,
+		 * we have to check those before this one
+		 */
+		next_head = after_or_end(where) ? in_tok->list.prev
+						: in_tok->list.next;
+		if (next_head == head)
+			break;
+		in_tok = list_entry(next_head, struct trailer_item, list);
+	} while (check_all);
+	return 1;
+}
+
+static char *apply_command(const char *command, const char *arg)
+{
+	struct strbuf cmd = STRBUF_INIT;
+	struct strbuf buf = STRBUF_INIT;
+	struct child_process cp = CHILD_PROCESS_INIT;
+	const char *argv[] = {NULL, NULL};
+	char *result;
+
+	strbuf_addstr(&cmd, command);
+	if (arg)
+		strbuf_replace(&cmd, TRAILER_ARG_STRING, arg);
+
+	argv[0] = cmd.buf;
+	cp.argv = argv;
+	cp.env = local_repo_env;
+	cp.no_stdin = 1;
+	cp.use_shell = 1;
+
+	if (capture_command(&cp, &buf, 1024)) {
+		error(_("running trailer command '%s' failed"), cmd.buf);
+		strbuf_release(&buf);
+		result = xstrdup("");
+	} else {
+		strbuf_trim(&buf);
+		result = strbuf_detach(&buf, NULL);
+	}
+
+	strbuf_release(&cmd);
+	return result;
+}
+
+static void apply_item_command(struct trailer_item *in_tok, struct arg_item *arg_tok)
+{
+	if (arg_tok->conf.command) {
+		const char *arg;
+		if (arg_tok->value && arg_tok->value[0]) {
+			arg = arg_tok->value;
+		} else {
+			if (in_tok && in_tok->value)
+				arg = xstrdup(in_tok->value);
+			else
+				arg = xstrdup("");
+		}
+		arg_tok->value = apply_command(arg_tok->conf.command, arg);
+		free((char *)arg);
+	}
+}
+
+static void apply_arg_if_exists(struct trailer_item *in_tok,
+				struct arg_item *arg_tok,
+				struct trailer_item *on_tok,
+				struct list_head *head)
+{
+	switch (arg_tok->conf.if_exists) {
+	case EXISTS_DO_NOTHING:
+		free_arg_item(arg_tok);
+		break;
+	case EXISTS_REPLACE:
+		apply_item_command(in_tok, arg_tok);
+		add_arg_to_input_list(on_tok, arg_tok);
+		list_del(&in_tok->list);
+		free_trailer_item(in_tok);
+		break;
+	case EXISTS_ADD:
+		apply_item_command(in_tok, arg_tok);
+		add_arg_to_input_list(on_tok, arg_tok);
+		break;
+	case EXISTS_ADD_IF_DIFFERENT:
+		apply_item_command(in_tok, arg_tok);
+		if (check_if_different(in_tok, arg_tok, 1, head))
+			add_arg_to_input_list(on_tok, arg_tok);
+		else
+			free_arg_item(arg_tok);
+		break;
+	case EXISTS_ADD_IF_DIFFERENT_NEIGHBOR:
+		apply_item_command(in_tok, arg_tok);
+		if (check_if_different(on_tok, arg_tok, 0, head))
+			add_arg_to_input_list(on_tok, arg_tok);
+		else
+			free_arg_item(arg_tok);
+		break;
+	default:
+		BUG("trailer.c: unhandled value %d",
+		    arg_tok->conf.if_exists);
+	}
+}
+
+static void apply_arg_if_missing(struct list_head *head,
+				 struct arg_item *arg_tok)
+{
+	enum trailer_where where;
+	struct trailer_item *to_add;
+
+	switch (arg_tok->conf.if_missing) {
+	case MISSING_DO_NOTHING:
+		free_arg_item(arg_tok);
+		break;
+	case MISSING_ADD:
+		where = arg_tok->conf.where;
+		apply_item_command(NULL, arg_tok);
+		to_add = trailer_from_arg(arg_tok);
+		if (after_or_end(where))
+			list_add_tail(&to_add->list, head);
+		else
+			list_add(&to_add->list, head);
+		break;
+	default:
+		BUG("trailer.c: unhandled value %d",
+		    arg_tok->conf.if_missing);
+	}
+}
+
+static int find_same_and_apply_arg(struct list_head *head,
+				   struct arg_item *arg_tok)
+{
+	struct list_head *pos;
+	struct trailer_item *in_tok;
+	struct trailer_item *on_tok;
+
+	enum trailer_where where = arg_tok->conf.where;
+	int middle = (where == WHERE_AFTER) || (where == WHERE_BEFORE);
+	int backwards = after_or_end(where);
+	struct trailer_item *start_tok;
+
+	if (list_empty(head))
+		return 0;
+
+	start_tok = list_entry(backwards ? head->prev : head->next,
+			       struct trailer_item,
+			       list);
+
+	list_for_each_dir(pos, head, backwards) {
+		in_tok = list_entry(pos, struct trailer_item, list);
+		if (!same_token(in_tok, arg_tok))
+			continue;
+		on_tok = middle ? in_tok : start_tok;
+		apply_arg_if_exists(in_tok, arg_tok, on_tok, head);
+		return 1;
+	}
+	return 0;
+}
+
+static void process_trailers_lists(struct list_head *head,
+				   struct list_head *arg_head)
+{
+	struct list_head *pos, *p;
+	struct arg_item *arg_tok;
+
+	list_for_each_safe(pos, p, arg_head) {
+		int applied = 0;
+		arg_tok = list_entry(pos, struct arg_item, list);
+
+		list_del(pos);
+
+		applied = find_same_and_apply_arg(head, arg_tok);
+
+		if (!applied)
+			apply_arg_if_missing(head, arg_tok);
+	}
+}
+
+int trailer_set_where(enum trailer_where *item, const char *value)
+{
+	if (!value)
+		*item = WHERE_DEFAULT;
+	else if (!strcasecmp("after", value))
+		*item = WHERE_AFTER;
+	else if (!strcasecmp("before", value))
+		*item = WHERE_BEFORE;
+	else if (!strcasecmp("end", value))
+		*item = WHERE_END;
+	else if (!strcasecmp("start", value))
+		*item = WHERE_START;
+	else
+		return -1;
+	return 0;
+}
+
+int trailer_set_if_exists(enum trailer_if_exists *item, const char *value)
+{
+	if (!value)
+		*item = EXISTS_DEFAULT;
+	else if (!strcasecmp("addIfDifferent", value))
+		*item = EXISTS_ADD_IF_DIFFERENT;
+	else if (!strcasecmp("addIfDifferentNeighbor", value))
+		*item = EXISTS_ADD_IF_DIFFERENT_NEIGHBOR;
+	else if (!strcasecmp("add", value))
+		*item = EXISTS_ADD;
+	else if (!strcasecmp("replace", value))
+		*item = EXISTS_REPLACE;
+	else if (!strcasecmp("doNothing", value))
+		*item = EXISTS_DO_NOTHING;
+	else
+		return -1;
+	return 0;
+}
+
+int trailer_set_if_missing(enum trailer_if_missing *item, const char *value)
+{
+	if (!value)
+		*item = MISSING_DEFAULT;
+	else if (!strcasecmp("doNothing", value))
+		*item = MISSING_DO_NOTHING;
+	else if (!strcasecmp("add", value))
+		*item = MISSING_ADD;
+	else
+		return -1;
+	return 0;
+}
+
+static void duplicate_conf(struct conf_info *dst, const struct conf_info *src)
+{
+	*dst = *src;
+	dst->name = xstrdup_or_null(src->name);
+	dst->key = xstrdup_or_null(src->key);
+	dst->command = xstrdup_or_null(src->command);
+}
+
+static struct arg_item *get_conf_item(const char *name)
+{
+	struct list_head *pos;
+	struct arg_item *item;
+
+	/* Look up item with same name */
+	list_for_each(pos, &conf_head) {
+		item = list_entry(pos, struct arg_item, list);
+		if (!strcasecmp(item->conf.name, name))
+			return item;
+	}
+
+	/* Item does not already exists, create it */
+	item = xcalloc(sizeof(*item), 1);
+	duplicate_conf(&item->conf, &default_conf_info);
+	item->conf.name = xstrdup(name);
+
+	list_add_tail(&item->list, &conf_head);
+
+	return item;
+}
+
+enum trailer_info_type { TRAILER_KEY, TRAILER_COMMAND, TRAILER_WHERE,
+			 TRAILER_IF_EXISTS, TRAILER_IF_MISSING };
+
+static struct {
+	const char *name;
+	enum trailer_info_type type;
+} trailer_config_items[] = {
+	{ "key", TRAILER_KEY },
+	{ "command", TRAILER_COMMAND },
+	{ "where", TRAILER_WHERE },
+	{ "ifexists", TRAILER_IF_EXISTS },
+	{ "ifmissing", TRAILER_IF_MISSING }
+};
+
+static int git_trailer_default_config(const char *conf_key, const char *value, void *cb)
+{
+	const char *trailer_item, *variable_name;
+
+	if (!skip_prefix(conf_key, "trailer.", &trailer_item))
+		return 0;
+
+	variable_name = strrchr(trailer_item, '.');
+	if (!variable_name) {
+		if (!strcmp(trailer_item, "where")) {
+			if (trailer_set_where(&default_conf_info.where,
+					      value) < 0)
+				warning(_("unknown value '%s' for key '%s'"),
+					value, conf_key);
+		} else if (!strcmp(trailer_item, "ifexists")) {
+			if (trailer_set_if_exists(&default_conf_info.if_exists,
+						  value) < 0)
+				warning(_("unknown value '%s' for key '%s'"),
+					value, conf_key);
+		} else if (!strcmp(trailer_item, "ifmissing")) {
+			if (trailer_set_if_missing(&default_conf_info.if_missing,
+						   value) < 0)
+				warning(_("unknown value '%s' for key '%s'"),
+					value, conf_key);
+		} else if (!strcmp(trailer_item, "separators")) {
+			separators = xstrdup(value);
+		}
+	}
+	return 0;
+}
+
+static int git_trailer_config(const char *conf_key, const char *value, void *cb)
+{
+	const char *trailer_item, *variable_name;
+	struct arg_item *item;
+	struct conf_info *conf;
+	char *name = NULL;
+	enum trailer_info_type type;
+	int i;
+
+	if (!skip_prefix(conf_key, "trailer.", &trailer_item))
+		return 0;
+
+	variable_name = strrchr(trailer_item, '.');
+	if (!variable_name)
+		return 0;
+
+	variable_name++;
+	for (i = 0; i < ARRAY_SIZE(trailer_config_items); i++) {
+		if (strcmp(trailer_config_items[i].name, variable_name))
+			continue;
+		name = xstrndup(trailer_item,  variable_name - trailer_item - 1);
+		type = trailer_config_items[i].type;
+		break;
+	}
+
+	if (!name)
+		return 0;
+
+	item = get_conf_item(name);
+	conf = &item->conf;
+	free(name);
+
+	switch (type) {
+	case TRAILER_KEY:
+		if (conf->key)
+			warning(_("more than one %s"), conf_key);
+		conf->key = xstrdup(value);
+		break;
+	case TRAILER_COMMAND:
+		if (conf->command)
+			warning(_("more than one %s"), conf_key);
+		conf->command = xstrdup(value);
+		break;
+	case TRAILER_WHERE:
+		if (trailer_set_where(&conf->where, value))
+			warning(_("unknown value '%s' for key '%s'"), value, conf_key);
+		break;
+	case TRAILER_IF_EXISTS:
+		if (trailer_set_if_exists(&conf->if_exists, value))
+			warning(_("unknown value '%s' for key '%s'"), value, conf_key);
+		break;
+	case TRAILER_IF_MISSING:
+		if (trailer_set_if_missing(&conf->if_missing, value))
+			warning(_("unknown value '%s' for key '%s'"), value, conf_key);
+		break;
+	default:
+		BUG("trailer.c: unhandled type %d", type);
+	}
+	return 0;
+}
+
+static void ensure_configured(void)
+{
+	if (configured)
+		return;
+
+	/* Default config must be setup first */
+	default_conf_info.where = WHERE_END;
+	default_conf_info.if_exists = EXISTS_ADD_IF_DIFFERENT_NEIGHBOR;
+	default_conf_info.if_missing = MISSING_ADD;
+	git_config(git_trailer_default_config, NULL);
+	git_config(git_trailer_config, NULL);
+	configured = 1;
+}
+
+static const char *token_from_item(struct arg_item *item, char *tok)
+{
+	if (item->conf.key)
+		return item->conf.key;
+	if (tok)
+		return tok;
+	return item->conf.name;
+}
+
+static int token_matches_item(const char *tok, struct arg_item *item, size_t tok_len)
+{
+	if (!strncasecmp(tok, item->conf.name, tok_len))
+		return 1;
+	return item->conf.key ? !strncasecmp(tok, item->conf.key, tok_len) : 0;
+}
+
+/*
+ * If the given line is of the form
+ * "<token><optional whitespace><separator>..." or "<separator>...", return the
+ * location of the separator. Otherwise, return -1.  The optional whitespace
+ * is allowed there primarily to allow things like "Bug #43" where <token> is
+ * "Bug" and <separator> is "#".
+ *
+ * The separator-starts-line case (in which this function returns 0) is
+ * distinguished from the non-well-formed-line case (in which this function
+ * returns -1) because some callers of this function need such a distinction.
+ */
+static ssize_t find_separator(const char *line, const char *separators)
+{
+	int whitespace_found = 0;
+	const char *c;
+	for (c = line; *c; c++) {
+		if (strchr(separators, *c))
+			return c - line;
+		if (!whitespace_found && (isalnum(*c) || *c == '-'))
+			continue;
+		if (c != line && (*c == ' ' || *c == '\t')) {
+			whitespace_found = 1;
+			continue;
+		}
+		break;
+	}
+	return -1;
+}
+
+/*
+ * Obtain the token, value, and conf from the given trailer.
+ *
+ * separator_pos must not be 0, since the token cannot be an empty string.
+ *
+ * If separator_pos is -1, interpret the whole trailer as a token.
+ */
+static void parse_trailer(struct strbuf *tok, struct strbuf *val,
+			 const struct conf_info **conf, const char *trailer,
+			 ssize_t separator_pos)
+{
+	struct arg_item *item;
+	size_t tok_len;
+	struct list_head *pos;
+
+	if (separator_pos != -1) {
+		strbuf_add(tok, trailer, separator_pos);
+		strbuf_trim(tok);
+		strbuf_addstr(val, trailer + separator_pos + 1);
+		strbuf_trim(val);
+	} else {
+		strbuf_addstr(tok, trailer);
+		strbuf_trim(tok);
+	}
+
+	/* Lookup if the token matches something in the config */
+	tok_len = token_len_without_separator(tok->buf, tok->len);
+	if (conf)
+		*conf = &default_conf_info;
+	list_for_each(pos, &conf_head) {
+		item = list_entry(pos, struct arg_item, list);
+		if (token_matches_item(tok->buf, item, tok_len)) {
+			char *tok_buf = strbuf_detach(tok, NULL);
+			if (conf)
+				*conf = &item->conf;
+			strbuf_addstr(tok, token_from_item(item, tok_buf));
+			free(tok_buf);
+			break;
+		}
+	}
+}
+
+static struct trailer_item *add_trailer_item(struct list_head *head, char *tok,
+					     char *val)
+{
+	struct trailer_item *new_item = xcalloc(sizeof(*new_item), 1);
+	new_item->token = tok;
+	new_item->value = val;
+	list_add_tail(&new_item->list, head);
+	return new_item;
+}
+
+static void add_arg_item(struct list_head *arg_head, char *tok, char *val,
+			 const struct conf_info *conf,
+			 const struct new_trailer_item *new_trailer_item)
+{
+	struct arg_item *new_item = xcalloc(sizeof(*new_item), 1);
+	new_item->token = tok;
+	new_item->value = val;
+	duplicate_conf(&new_item->conf, conf);
+	if (new_trailer_item) {
+		if (new_trailer_item->where != WHERE_DEFAULT)
+			new_item->conf.where = new_trailer_item->where;
+		if (new_trailer_item->if_exists != EXISTS_DEFAULT)
+			new_item->conf.if_exists = new_trailer_item->if_exists;
+		if (new_trailer_item->if_missing != MISSING_DEFAULT)
+			new_item->conf.if_missing = new_trailer_item->if_missing;
+	}
+	list_add_tail(&new_item->list, arg_head);
+}
+
+static void process_command_line_args(struct list_head *arg_head,
+				      struct list_head *new_trailer_head)
+{
+	struct arg_item *item;
+	struct strbuf tok = STRBUF_INIT;
+	struct strbuf val = STRBUF_INIT;
+	const struct conf_info *conf;
+	struct list_head *pos;
+
+	/*
+	 * In command-line arguments, '=' is accepted (in addition to the
+	 * separators that are defined).
+	 */
+	char *cl_separators = xstrfmt("=%s", separators);
+
+	/* Add an arg item for each configured trailer with a command */
+	list_for_each(pos, &conf_head) {
+		item = list_entry(pos, struct arg_item, list);
+		if (item->conf.command)
+			add_arg_item(arg_head,
+				     xstrdup(token_from_item(item, NULL)),
+				     xstrdup(""),
+				     &item->conf, NULL);
+	}
+
+	/* Add an arg item for each trailer on the command line */
+	list_for_each(pos, new_trailer_head) {
+		struct new_trailer_item *tr =
+			list_entry(pos, struct new_trailer_item, list);
+		ssize_t separator_pos = find_separator(tr->text, cl_separators);
+
+		if (separator_pos == 0) {
+			struct strbuf sb = STRBUF_INIT;
+			strbuf_addstr(&sb, tr->text);
+			strbuf_trim(&sb);
+			error(_("empty trailer token in trailer '%.*s'"),
+			      (int) sb.len, sb.buf);
+			strbuf_release(&sb);
+		} else {
+			parse_trailer(&tok, &val, &conf, tr->text,
+				      separator_pos);
+			add_arg_item(arg_head,
+				     strbuf_detach(&tok, NULL),
+				     strbuf_detach(&val, NULL),
+				     conf, tr);
+		}
+	}
+
+	free(cl_separators);
+}
+
+static void read_input_file(struct strbuf *sb, const char *file)
+{
+	if (file) {
+		if (strbuf_read_file(sb, file, 0) < 0)
+			die_errno(_("could not read input file '%s'"), file);
+	} else {
+		if (strbuf_read(sb, fileno(stdin), 0) < 0)
+			die_errno(_("could not read from stdin"));
+	}
+}
+
+static const char *next_line(const char *str)
+{
+	const char *nl = strchrnul(str, '\n');
+	return nl + !!*nl;
+}
+
+/*
+ * Return the position of the start of the last line. If len is 0, return -1.
+ */
+static ssize_t last_line(const char *buf, size_t len)
+{
+	ssize_t i;
+	if (len == 0)
+		return -1;
+	if (len == 1)
+		return 0;
+	/*
+	 * Skip the last character (in addition to the null terminator),
+	 * because if the last character is a newline, it is considered as part
+	 * of the last line anyway.
+	 */
+	i = len - 2;
+
+	for (; i >= 0; i--) {
+		if (buf[i] == '\n')
+			return i + 1;
+	}
+	return 0;
+}
+
+/*
+ * Return the position of the start of the patch or the length of str if there
+ * is no patch in the message.
+ */
+static size_t find_patch_start(const char *str)
+{
+	const char *s;
+
+	for (s = str; *s; s = next_line(s)) {
+		const char *v;
+
+		if (skip_prefix(s, "---", &v) && isspace(*v))
+			return s - str;
+	}
+
+	return s - str;
+}
+
+/*
+ * Return the position of the first trailer line or len if there are no
+ * trailers.
+ */
+static size_t find_trailer_start(const char *buf, size_t len)
+{
+	const char *s;
+	ssize_t end_of_title, l;
+	int only_spaces = 1;
+	int recognized_prefix = 0, trailer_lines = 0, non_trailer_lines = 0;
+	/*
+	 * Number of possible continuation lines encountered. This will be
+	 * reset to 0 if we encounter a trailer (since those lines are to be
+	 * considered continuations of that trailer), and added to
+	 * non_trailer_lines if we encounter a non-trailer (since those lines
+	 * are to be considered non-trailers).
+	 */
+	int possible_continuation_lines = 0;
+
+	/* The first paragraph is the title and cannot be trailers */
+	for (s = buf; s < buf + len; s = next_line(s)) {
+		if (s[0] == comment_line_char)
+			continue;
+		if (is_blank_line(s))
+			break;
+	}
+	end_of_title = s - buf;
+
+	/*
+	 * Get the start of the trailers by looking starting from the end for a
+	 * blank line before a set of non-blank lines that (i) are all
+	 * trailers, or (ii) contains at least one Git-generated trailer and
+	 * consists of at least 25% trailers.
+	 */
+	for (l = last_line(buf, len);
+	     l >= end_of_title;
+	     l = last_line(buf, l)) {
+		const char *bol = buf + l;
+		const char **p;
+		ssize_t separator_pos;
+
+		if (bol[0] == comment_line_char) {
+			non_trailer_lines += possible_continuation_lines;
+			possible_continuation_lines = 0;
+			continue;
+		}
+		if (is_blank_line(bol)) {
+			if (only_spaces)
+				continue;
+			non_trailer_lines += possible_continuation_lines;
+			if (recognized_prefix &&
+			    trailer_lines * 3 >= non_trailer_lines)
+				return next_line(bol) - buf;
+			else if (trailer_lines && !non_trailer_lines)
+				return next_line(bol) - buf;
+			return len;
+		}
+		only_spaces = 0;
+
+		for (p = git_generated_prefixes; *p; p++) {
+			if (starts_with(bol, *p)) {
+				trailer_lines++;
+				possible_continuation_lines = 0;
+				recognized_prefix = 1;
+				goto continue_outer_loop;
+			}
+		}
+
+		separator_pos = find_separator(bol, separators);
+		if (separator_pos >= 1 && !isspace(bol[0])) {
+			struct list_head *pos;
+
+			trailer_lines++;
+			possible_continuation_lines = 0;
+			if (recognized_prefix)
+				continue;
+			list_for_each(pos, &conf_head) {
+				struct arg_item *item;
+				item = list_entry(pos, struct arg_item, list);
+				if (token_matches_item(bol, item,
+						       separator_pos)) {
+					recognized_prefix = 1;
+					break;
+				}
+			}
+		} else if (isspace(bol[0]))
+			possible_continuation_lines++;
+		else {
+			non_trailer_lines++;
+			non_trailer_lines += possible_continuation_lines;
+			possible_continuation_lines = 0;
+		}
+continue_outer_loop:
+		;
+	}
+
+	return len;
+}
+
+/* Return the position of the end of the trailers. */
+static size_t find_trailer_end(const char *buf, size_t len)
+{
+	return len - ignore_non_trailer(buf, len);
+}
+
+static int ends_with_blank_line(const char *buf, size_t len)
+{
+	ssize_t ll = last_line(buf, len);
+	if (ll < 0)
+		return 0;
+	return is_blank_line(buf + ll);
+}
+
+static void unfold_value(struct strbuf *val)
+{
+	struct strbuf out = STRBUF_INIT;
+	size_t i;
+
+	strbuf_grow(&out, val->len);
+	i = 0;
+	while (i < val->len) {
+		char c = val->buf[i++];
+		if (c == '\n') {
+			/* Collapse continuation down to a single space. */
+			while (i < val->len && isspace(val->buf[i]))
+				i++;
+			strbuf_addch(&out, ' ');
+		} else {
+			strbuf_addch(&out, c);
+		}
+	}
+
+	/* Empty lines may have left us with whitespace cruft at the edges */
+	strbuf_trim(&out);
+
+	/* output goes back to val as if we modified it in-place */
+	strbuf_swap(&out, val);
+	strbuf_release(&out);
+}
+
+static size_t process_input_file(FILE *outfile,
+				 const char *str,
+				 struct list_head *head,
+				 const struct process_trailer_options *opts)
+{
+	struct trailer_info info;
+	struct strbuf tok = STRBUF_INIT;
+	struct strbuf val = STRBUF_INIT;
+	size_t i;
+
+	trailer_info_get(&info, str, opts);
+
+	/* Print lines before the trailers as is */
+	if (!opts->only_trailers)
+		fwrite(str, 1, info.trailer_start - str, outfile);
+
+	if (!opts->only_trailers && !info.blank_line_before_trailer)
+		fprintf(outfile, "\n");
+
+	for (i = 0; i < info.trailer_nr; i++) {
+		int separator_pos;
+		char *trailer = info.trailers[i];
+		if (trailer[0] == comment_line_char)
+			continue;
+		separator_pos = find_separator(trailer, separators);
+		if (separator_pos >= 1) {
+			parse_trailer(&tok, &val, NULL, trailer,
+				      separator_pos);
+			if (opts->unfold)
+				unfold_value(&val);
+			add_trailer_item(head,
+					 strbuf_detach(&tok, NULL),
+					 strbuf_detach(&val, NULL));
+		} else if (!opts->only_trailers) {
+			strbuf_addstr(&val, trailer);
+			strbuf_strip_suffix(&val, "\n");
+			add_trailer_item(head,
+					 NULL,
+					 strbuf_detach(&val, NULL));
+		}
+	}
+
+	trailer_info_release(&info);
+
+	return info.trailer_end - str;
+}
+
+static void free_all(struct list_head *head)
+{
+	struct list_head *pos, *p;
+	list_for_each_safe(pos, p, head) {
+		list_del(pos);
+		free_trailer_item(list_entry(pos, struct trailer_item, list));
+	}
+}
+
+static struct tempfile *trailers_tempfile;
+
+static FILE *create_in_place_tempfile(const char *file)
+{
+	struct stat st;
+	struct strbuf filename_template = STRBUF_INIT;
+	const char *tail;
+	FILE *outfile;
+
+	if (stat(file, &st))
+		die_errno(_("could not stat %s"), file);
+	if (!S_ISREG(st.st_mode))
+		die(_("file %s is not a regular file"), file);
+	if (!(st.st_mode & S_IWUSR))
+		die(_("file %s is not writable by user"), file);
+
+	/* Create temporary file in the same directory as the original */
+	tail = strrchr(file, '/');
+	if (tail != NULL)
+		strbuf_add(&filename_template, file, tail - file + 1);
+	strbuf_addstr(&filename_template, "git-interpret-trailers-XXXXXX");
+
+	trailers_tempfile = xmks_tempfile_m(filename_template.buf, st.st_mode);
+	strbuf_release(&filename_template);
+	outfile = fdopen_tempfile(trailers_tempfile, "w");
+	if (!outfile)
+		die_errno(_("could not open temporary file"));
+
+	return outfile;
+}
+
+void process_trailers(const char *file,
+		      const struct process_trailer_options *opts,
+		      struct list_head *new_trailer_head)
+{
+	LIST_HEAD(head);
+	struct strbuf sb = STRBUF_INIT;
+	size_t trailer_end;
+	FILE *outfile = stdout;
+
+	ensure_configured();
+
+	read_input_file(&sb, file);
+
+	if (opts->in_place)
+		outfile = create_in_place_tempfile(file);
+
+	/* Print the lines before the trailers */
+	trailer_end = process_input_file(outfile, sb.buf, &head, opts);
+
+	if (!opts->only_input) {
+		LIST_HEAD(arg_head);
+		process_command_line_args(&arg_head, new_trailer_head);
+		process_trailers_lists(&head, &arg_head);
+	}
+
+	print_all(outfile, &head, opts);
+
+	free_all(&head);
+
+	/* Print the lines after the trailers as is */
+	if (!opts->only_trailers)
+		fwrite(sb.buf + trailer_end, 1, sb.len - trailer_end, outfile);
+
+	if (opts->in_place)
+		if (rename_tempfile(&trailers_tempfile, file))
+			die_errno(_("could not rename temporary file to %s"), file);
+
+	strbuf_release(&sb);
+}
+
+void trailer_info_get(struct trailer_info *info, const char *str,
+		      const struct process_trailer_options *opts)
+{
+	int patch_start, trailer_end, trailer_start;
+	struct strbuf **trailer_lines, **ptr;
+	char **trailer_strings = NULL;
+	size_t nr = 0, alloc = 0;
+	char **last = NULL;
+
+	ensure_configured();
+
+	if (opts->no_divider)
+		patch_start = strlen(str);
+	else
+		patch_start = find_patch_start(str);
+
+	trailer_end = find_trailer_end(str, patch_start);
+	trailer_start = find_trailer_start(str, trailer_end);
+
+	trailer_lines = strbuf_split_buf(str + trailer_start,
+					 trailer_end - trailer_start,
+					 '\n',
+					 0);
+	for (ptr = trailer_lines; *ptr; ptr++) {
+		if (last && isspace((*ptr)->buf[0])) {
+			struct strbuf sb = STRBUF_INIT;
+			strbuf_attach(&sb, *last, strlen(*last), strlen(*last));
+			strbuf_addbuf(&sb, *ptr);
+			*last = strbuf_detach(&sb, NULL);
+			continue;
+		}
+		ALLOC_GROW(trailer_strings, nr + 1, alloc);
+		trailer_strings[nr] = strbuf_detach(*ptr, NULL);
+		last = find_separator(trailer_strings[nr], separators) >= 1
+			? &trailer_strings[nr]
+			: NULL;
+		nr++;
+	}
+	strbuf_list_free(trailer_lines);
+
+	info->blank_line_before_trailer = ends_with_blank_line(str,
+							       trailer_start);
+	info->trailer_start = str + trailer_start;
+	info->trailer_end = str + trailer_end;
+	info->trailers = trailer_strings;
+	info->trailer_nr = nr;
+}
+
+void trailer_info_release(struct trailer_info *info)
+{
+	size_t i;
+	for (i = 0; i < info->trailer_nr; i++)
+		free(info->trailers[i]);
+	free(info->trailers);
+}
+
+static void format_trailer_info(struct strbuf *out,
+				const struct trailer_info *info,
+				const struct process_trailer_options *opts)
+{
+	size_t origlen = out->len;
+	size_t i;
+
+	/* If we want the whole block untouched, we can take the fast path. */
+	if (!opts->only_trailers && !opts->unfold && !opts->filter && !opts->separator) {
+		strbuf_add(out, info->trailer_start,
+			   info->trailer_end - info->trailer_start);
+		return;
+	}
+
+	for (i = 0; i < info->trailer_nr; i++) {
+		char *trailer = info->trailers[i];
+		ssize_t separator_pos = find_separator(trailer, separators);
+
+		if (separator_pos >= 1) {
+			struct strbuf tok = STRBUF_INIT;
+			struct strbuf val = STRBUF_INIT;
+
+			parse_trailer(&tok, &val, NULL, trailer, separator_pos);
+			if (!opts->filter || opts->filter(&tok, opts->filter_data)) {
+				if (opts->unfold)
+					unfold_value(&val);
+
+				if (opts->separator && out->len != origlen)
+					strbuf_addbuf(out, opts->separator);
+				if (!opts->value_only)
+					strbuf_addf(out, "%s: ", tok.buf);
+				strbuf_addbuf(out, &val);
+				if (!opts->separator)
+					strbuf_addch(out, '\n');
+			}
+			strbuf_release(&tok);
+			strbuf_release(&val);
+
+		} else if (!opts->only_trailers) {
+			if (opts->separator && out->len != origlen) {
+				strbuf_addbuf(out, opts->separator);
+			}
+			strbuf_addstr(out, trailer);
+			if (opts->separator) {
+				strbuf_rtrim(out);
+			}
+		}
+	}
+
+}
+
+void format_trailers_from_commit(struct strbuf *out, const char *msg,
+				 const struct process_trailer_options *opts)
+{
+	struct trailer_info info;
+
+	trailer_info_get(&info, msg, opts);
+	format_trailer_info(out, &info, opts);
+	trailer_info_release(&info);
+}