Merge branch 'rr/revert-cherry-pick-continue'

* rr/revert-cherry-pick-continue:
  builtin/revert.c: make commit_list_append() static
  revert: Propagate errors upwards from do_pick_commit
  revert: Introduce --continue to continue the operation
  revert: Don't implicitly stomp pending sequencer operation
  revert: Remove sequencer state when no commits are pending
  reset: Make reset remove the sequencer state
  revert: Introduce --reset to remove sequencer state
  revert: Make pick_commits functionally act on a commit list
  revert: Save command-line options for continuing operation
  revert: Save data for continuing after conflict resolution
  revert: Don't create invalid replay_opts in parse_args
  revert: Separate cmdline parsing from functional code
  revert: Introduce struct to keep command-line options
  revert: Eliminate global "commit" variable
  revert: Rename no_replay to record_origin
  revert: Don't check lone argument in get_encoding
  revert: Simplify and inline add_message_to_msg
  config: Introduce functions to write non-standard file
  advice: Introduce error_resolve_conflict

1 files changed, 583 insertions, 154 deletions

diff --git a/builtin/revert.c b/builtin/revert.c
index 3117776c2c..ba27cf15ee 100644
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -13,6 +13,8 @@
 #include "rerere.h"
 #include "merge-recursive.h"
 #include "refs.h"
+#include "dir.h"
+#include "sequencer.h"
 
 /*
  * This implements the builtins revert and cherry-pick.
@@ -27,85 +29,189 @@
 
 static const char * const revert_usage[] = {
 	"git revert [options] <commit-ish>",
+	"git revert <subcommand>",
 	NULL
 };
 
 static const char * const cherry_pick_usage[] = {
 	"git cherry-pick [options] <commit-ish>",
+	"git cherry-pick <subcommand>",
 	NULL
 };
 
-static int edit, no_replay, no_commit, mainline, signoff, allow_ff;
-static enum { REVERT, CHERRY_PICK } action;
-static struct commit *commit;
-static int commit_argc;
-static const char **commit_argv;
-static int allow_rerere_auto;
-
-static const char *me;
-
-/* Merge strategy. */
-static const char *strategy;
-static const char **xopts;
-static size_t xopts_nr, xopts_alloc;
+enum replay_action { REVERT, CHERRY_PICK };
+enum replay_subcommand { REPLAY_NONE, REPLAY_RESET, REPLAY_CONTINUE };
+
+struct replay_opts {
+	enum replay_action action;
+	enum replay_subcommand subcommand;
+
+	/* Boolean options */
+	int edit;
+	int record_origin;
+	int no_commit;
+	int signoff;
+	int allow_ff;
+	int allow_rerere_auto;
+
+	int mainline;
+	int commit_argc;
+	const char **commit_argv;
+
+	/* Merge strategy */
+	const char *strategy;
+	const char **xopts;
+	size_t xopts_nr, xopts_alloc;
+};
 
 #define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"
 
+static const char *action_name(const struct replay_opts *opts)
+{
+	return opts->action == REVERT ? "revert" : "cherry-pick";
+}
+
 static char *get_encoding(const char *message);
 
-static const char * const *revert_or_cherry_pick_usage(void)
+static const char * const *revert_or_cherry_pick_usage(struct replay_opts *opts)
 {
-	return action == REVERT ? revert_usage : cherry_pick_usage;
+	return opts->action == REVERT ? revert_usage : cherry_pick_usage;
 }
 
 static int option_parse_x(const struct option *opt,
 			  const char *arg, int unset)
 {
+	struct replay_opts **opts_ptr = opt->value;
+	struct replay_opts *opts = *opts_ptr;
+
 	if (unset)
 		return 0;
 
-	ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
-	xopts[xopts_nr++] = xstrdup(arg);
+	ALLOC_GROW(opts->xopts, opts->xopts_nr + 1, opts->xopts_alloc);
+	opts->xopts[opts->xopts_nr++] = xstrdup(arg);
 	return 0;
 }
 
-static void parse_args(int argc, const char **argv)
+static void verify_opt_compatible(const char *me, const char *base_opt, ...)
+{
+	const char *this_opt;
+	va_list ap;
+
+	va_start(ap, base_opt);
+	while ((this_opt = va_arg(ap, const char *))) {
+		if (va_arg(ap, int))
+			break;
+	}
+	va_end(ap);
+
+	if (this_opt)
+		die(_("%s: %s cannot be used with %s"), me, this_opt, base_opt);
+}
+
+static void verify_opt_mutually_compatible(const char *me, ...)
+{
+	const char *opt1, *opt2;
+	va_list ap;
+
+	va_start(ap, me);
+	while ((opt1 = va_arg(ap, const char *))) {
+		if (va_arg(ap, int))
+			break;
+	}
+	if (opt1) {
+		while ((opt2 = va_arg(ap, const char *))) {
+			if (va_arg(ap, int))
+				break;
+		}
+	}
+
+	if (opt1 && opt2)
+		die(_("%s: %s cannot be used with %s"),	me, opt1, opt2);
+}
+
+static void parse_args(int argc, const char **argv, struct replay_opts *opts)
 {
-	const char * const * usage_str = revert_or_cherry_pick_usage();
+	const char * const * usage_str = revert_or_cherry_pick_usage(opts);
+	const char *me = action_name(opts);
 	int noop;
+	int reset = 0;
+	int contin = 0;
 	struct option options[] = {
-		OPT_BOOLEAN('n', "no-commit", &no_commit, "don't automatically commit"),
-		OPT_BOOLEAN('e', "edit", &edit, "edit the commit message"),
+		OPT_BOOLEAN(0, "reset", &reset, "forget the current operation"),
+		OPT_BOOLEAN(0, "continue", &contin, "continue the current operation"),
+		OPT_BOOLEAN('n', "no-commit", &opts->no_commit, "don't automatically commit"),
+		OPT_BOOLEAN('e', "edit", &opts->edit, "edit the commit message"),
 		{ OPTION_BOOLEAN, 'r', NULL, &noop, NULL, "no-op (backward compatibility)",
 		  PARSE_OPT_NOARG | PARSE_OPT_HIDDEN, NULL, 0 },
-		OPT_BOOLEAN('s', "signoff", &signoff, "add Signed-off-by:"),
-		OPT_INTEGER('m', "mainline", &mainline, "parent number"),
-		OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
-		OPT_STRING(0, "strategy", &strategy, "strategy", "merge strategy"),
-		OPT_CALLBACK('X', "strategy-option", &xopts, "option",
+		OPT_BOOLEAN('s', "signoff", &opts->signoff, "add Signed-off-by:"),
+		OPT_INTEGER('m', "mainline", &opts->mainline, "parent number"),
+		OPT_RERERE_AUTOUPDATE(&opts->allow_rerere_auto),
+		OPT_STRING(0, "strategy", &opts->strategy, "strategy", "merge strategy"),
+		OPT_CALLBACK('X', "strategy-option", &opts, "option",
 			"option for merge strategy", option_parse_x),
 		OPT_END(),
 		OPT_END(),
 		OPT_END(),
 	};
 
-	if (action == CHERRY_PICK) {
+	if (opts->action == CHERRY_PICK) {
 		struct option cp_extra[] = {
-			OPT_BOOLEAN('x', NULL, &no_replay, "append commit name"),
-			OPT_BOOLEAN(0, "ff", &allow_ff, "allow fast-forward"),
+			OPT_BOOLEAN('x', NULL, &opts->record_origin, "append commit name"),
+			OPT_BOOLEAN(0, "ff", &opts->allow_ff, "allow fast-forward"),
 			OPT_END(),
 		};
 		if (parse_options_concat(options, ARRAY_SIZE(options), cp_extra))
 			die(_("program error"));
 	}
 
-	commit_argc = parse_options(argc, argv, NULL, options, usage_str,
-				    PARSE_OPT_KEEP_ARGV0 |
-				    PARSE_OPT_KEEP_UNKNOWN);
-	if (commit_argc < 2)
+	opts->commit_argc = parse_options(argc, argv, NULL, options, usage_str,
+					PARSE_OPT_KEEP_ARGV0 |
+					PARSE_OPT_KEEP_UNKNOWN);
+
+	/* Check for incompatible subcommands */
+	verify_opt_mutually_compatible(me,
+				"--reset", reset,
+				"--continue", contin,
+				NULL);
+
+	/* Set the subcommand */
+	if (reset)
+		opts->subcommand = REPLAY_RESET;
+	else if (contin)
+		opts->subcommand = REPLAY_CONTINUE;
+	else
+		opts->subcommand = REPLAY_NONE;
+
+	/* Check for incompatible command line arguments */
+	if (opts->subcommand != REPLAY_NONE) {
+		char *this_operation;
+		if (opts->subcommand == REPLAY_RESET)
+			this_operation = "--reset";
+		else
+			this_operation = "--continue";
+
+		verify_opt_compatible(me, this_operation,
+				"--no-commit", opts->no_commit,
+				"--signoff", opts->signoff,
+				"--mainline", opts->mainline,
+				"--strategy", opts->strategy ? 1 : 0,
+				"--strategy-option", opts->xopts ? 1 : 0,
+				"-x", opts->record_origin,
+				"--ff", opts->allow_ff,
+				NULL);
+	}
+
+	else if (opts->commit_argc < 2)
 		usage_with_options(usage_str, options);
 
-	commit_argv = argv;
+	if (opts->allow_ff)
+		verify_opt_compatible(me, "--ff",
+				"--signoff", opts->signoff,
+				"--no-commit", opts->no_commit,
+				"-x", opts->record_origin,
+				"--edit", opts->edit,
+				NULL);
+	opts->commit_argv = argv;
 }
 
 struct commit_message {
@@ -116,25 +222,25 @@ struct commit_message {
 	const char *message;
 };
 
-static int get_message(const char *raw_message, struct commit_message *out)
+static int get_message(struct commit *commit, struct commit_message *out)
 {
 	const char *encoding;
 	const char *abbrev, *subject;
 	int abbrev_len, subject_len;
 	char *q;
 
-	if (!raw_message)
+	if (!commit->buffer)
 		return -1;
-	encoding = get_encoding(raw_message);
+	encoding = get_encoding(commit->buffer);
 	if (!encoding)
 		encoding = "UTF-8";
 	if (!git_commit_encoding)
 		git_commit_encoding = "UTF-8";
 
 	out->reencoded_message = NULL;
-	out->message = raw_message;
+	out->message = commit->buffer;
 	if (strcmp(encoding, git_commit_encoding))
-		out->reencoded_message = reencode_string(raw_message,
+		out->reencoded_message = reencode_string(commit->buffer,
 					git_commit_encoding, encoding);
 	if (out->reencoded_message)
 		out->message = out->reencoded_message;
@@ -167,9 +273,6 @@ static char *get_encoding(const char *message)
 {
 	const char *p = message, *eol;
 
-	if (!p)
-		die (_("Could not read commit message of %s"),
-				sha1_to_hex(commit->object.sha1));
 	while (*p && *p != '\n') {
 		for (eol = p + 1; *eol && *eol != '\n'; eol++)
 			; /* do nothing */
@@ -185,20 +288,7 @@ static char *get_encoding(const char *message)
 	return NULL;
 }
 
-static void add_message_to_msg(struct strbuf *msgbuf, const char *message)
-{
-	const char *p = message;
-	while (*p && (*p != '\n' || p[1] != '\n'))
-		p++;
-
-	if (!*p)
-		strbuf_addstr(msgbuf, sha1_to_hex(commit->object.sha1));
-
-	p += 2;
-	strbuf_addstr(msgbuf, p);
-}
-
-static void write_cherry_pick_head(void)
+static void write_cherry_pick_head(struct commit *commit)
 {
 	int fd;
 	struct strbuf buf = STRBUF_INIT;
@@ -214,15 +304,6 @@ static void write_cherry_pick_head(void)
 	strbuf_release(&buf);
 }
 
-static void advise(const char *advice, ...)
-{
-	va_list params;
-
-	va_start(params, advice);
-	vreportf("hint: ", advice, params);
-	va_end(params);
-}
-
 static void print_advice(void)
 {
 	char *msg = getenv("GIT_CHERRY_PICK_HELP");
@@ -261,25 +342,20 @@ static struct tree *empty_tree(void)
 	return lookup_tree((const unsigned char *)EMPTY_TREE_SHA1_BIN);
 }
 
-static NORETURN void die_dirty_index(const char *me)
+static int error_dirty_index(struct replay_opts *opts)
 {
-	if (read_cache_unmerged()) {
-		die_resolve_conflict(me);
-	} else {
-		if (advice_commit_before_merge) {
-			if (action == REVERT)
-				die(_("Your local changes would be overwritten by revert.\n"
-					  "Please, commit your changes or stash them to proceed."));
-			else
-				die(_("Your local changes would be overwritten by cherry-pick.\n"
-					  "Please, commit your changes or stash them to proceed."));
-		} else {
-			if (action == REVERT)
-				die(_("Your local changes would be overwritten by revert.\n"));
-			else
-				die(_("Your local changes would be overwritten by cherry-pick.\n"));
-		}
-	}
+	if (read_cache_unmerged())
+		return error_resolve_conflict(action_name(opts));
+
+	/* Different translation strings for cherry-pick and revert */
+	if (opts->action == CHERRY_PICK)
+		error(_("Your local changes would be overwritten by cherry-pick."));
+	else
+		error(_("Your local changes would be overwritten by revert."));
+
+	if (advice_commit_before_merge)
+		advise(_("Commit your changes or stash them to proceed."));
+	return -1;
 }
 
 static int fast_forward_to(const unsigned char *to, const unsigned char *from)
@@ -295,7 +371,8 @@ static int fast_forward_to(const unsigned char *to, const unsigned char *from)
 
 static int do_recursive_merge(struct commit *base, struct commit *next,
 			      const char *base_label, const char *next_label,
-			      unsigned char *head, struct strbuf *msgbuf)
+			      unsigned char *head, struct strbuf *msgbuf,
+			      struct replay_opts *opts)
 {
 	struct merge_options o;
 	struct tree *result, *next_tree, *base_tree, *head_tree;
@@ -316,7 +393,7 @@ static int do_recursive_merge(struct commit *base, struct commit *next,
 	next_tree = next ? next->tree : empty_tree();
 	base_tree = base ? base->tree : empty_tree();
 
-	for (xopt = xopts; xopt != xopts + xopts_nr; xopt++)
+	for (xopt = opts->xopts; xopt != opts->xopts + opts->xopts_nr; xopt++)
 		parse_merge_opt(&o, *xopt);
 
 	clean = merge_trees(&o,
@@ -327,7 +404,7 @@ static int do_recursive_merge(struct commit *base, struct commit *next,
 	    (write_cache(index_fd, active_cache, active_nr) ||
 	     commit_locked_index(&index_lock)))
 		/* TRANSLATORS: %s will be "revert" or "cherry-pick" */
-		die(_("%s: Unable to write new index file"), me);
+		die(_("%s: Unable to write new index file"), action_name(opts));
 	rollback_lock_file(&index_lock);
 
 	if (!clean) {
@@ -356,7 +433,7 @@ static int do_recursive_merge(struct commit *base, struct commit *next,
  * If we are revert, or if our cherry-pick results in a hand merge,
  * we had better say that the current user is responsible for that.
  */
-static int run_git_commit(const char *defmsg)
+static int run_git_commit(const char *defmsg, struct replay_opts *opts)
 {
 	/* 6 is max possible length of our args array including NULL */
 	const char *args[6];
@@ -364,9 +441,9 @@ static int run_git_commit(const char *defmsg)
 
 	args[i++] = "commit";
 	args[i++] = "-n";
-	if (signoff)
+	if (opts->signoff)
 		args[i++] = "-s";
-	if (!edit) {
+	if (!opts->edit) {
 		args[i++] = "-F";
 		args[i++] = defmsg;
 	}
@@ -375,7 +452,7 @@ static int run_git_commit(const char *defmsg)
 	return run_command_v_opt(args, RUN_GIT_CMD);
 }
 
-static int do_pick_commit(void)
+static int do_pick_commit(struct commit *commit, struct replay_opts *opts)
 {
 	unsigned char head[20];
 	struct commit *base, *next, *parent;
@@ -385,7 +462,7 @@ static int do_pick_commit(void)
 	struct strbuf msgbuf = STRBUF_INIT;
 	int res;
 
-	if (no_commit) {
+	if (opts->no_commit) {
 		/*
 		 * We do not intend to commit immediately.  We just want to
 		 * merge the differences in, so let's compute the tree
@@ -396,9 +473,9 @@ static int do_pick_commit(void)
 			die (_("Your index file is unmerged."));
 	} else {
 		if (get_sha1("HEAD", head))
-			die (_("You do not have a valid HEAD"));
+			return error(_("You do not have a valid HEAD"));
 		if (index_differs_from("HEAD", 0))
-			die_dirty_index(me);
+			return error_dirty_index(opts);
 	}
 	discard_cache();
 
@@ -410,36 +487,36 @@ static int do_pick_commit(void)
 		int cnt;
 		struct commit_list *p;
 
-		if (!mainline)
-			die(_("Commit %s is a merge but no -m option was given."),
-			    sha1_to_hex(commit->object.sha1));
+		if (!opts->mainline)
+			return error(_("Commit %s is a merge but no -m option was given."),
+				sha1_to_hex(commit->object.sha1));
 
 		for (cnt = 1, p = commit->parents;
-		     cnt != mainline && p;
+		     cnt != opts->mainline && p;
 		     cnt++)
 			p = p->next;
-		if (cnt != mainline || !p)
-			die(_("Commit %s does not have parent %d"),
-			    sha1_to_hex(commit->object.sha1), mainline);
+		if (cnt != opts->mainline || !p)
+			return error(_("Commit %s does not have parent %d"),
+				sha1_to_hex(commit->object.sha1), opts->mainline);
 		parent = p->item;
-	} else if (0 < mainline)
-		die(_("Mainline was specified but commit %s is not a merge."),
-		    sha1_to_hex(commit->object.sha1));
+	} else if (0 < opts->mainline)
+		return error(_("Mainline was specified but commit %s is not a merge."),
+			sha1_to_hex(commit->object.sha1));
 	else
 		parent = commit->parents->item;
 
-	if (allow_ff && parent && !hashcmp(parent->object.sha1, head))
+	if (opts->allow_ff && parent && !hashcmp(parent->object.sha1, head))
 		return fast_forward_to(commit->object.sha1, head);
 
 	if (parent && parse_commit(parent) < 0)
 		/* TRANSLATORS: The first %s will be "revert" or
 		   "cherry-pick", the second %s a SHA1 */
-		die(_("%s: cannot parse parent commit %s"),
-		    me, sha1_to_hex(parent->object.sha1));
+		return error(_("%s: cannot parse parent commit %s"),
+			action_name(opts), sha1_to_hex(parent->object.sha1));
 
-	if (get_message(commit->buffer, &msg) != 0)
-		die(_("Cannot get commit message for %s"),
-				sha1_to_hex(commit->object.sha1));
+	if (get_message(commit, &msg) != 0)
+		return error(_("Cannot get commit message for %s"),
+			sha1_to_hex(commit->object.sha1));
 
 	/*
 	 * "commit" is an existing commit.  We would want to apply
@@ -450,7 +527,7 @@ static int do_pick_commit(void)
 
 	defmsg = git_pathdup("MERGE_MSG");
 
-	if (action == REVERT) {
+	if (opts->action == REVERT) {
 		base = commit;
 		base_label = msg.label;
 		next = parent;
@@ -466,23 +543,36 @@ static int do_pick_commit(void)
 		}
 		strbuf_addstr(&msgbuf, ".\n");
 	} else {
+		const char *p;
+
 		base = parent;
 		base_label = msg.parent_label;
 		next = commit;
 		next_label = msg.label;
-		add_message_to_msg(&msgbuf, msg.message);
-		if (no_replay) {
+
+		/*
+		 * Append the commit log message to msgbuf; it starts
+		 * after the tree, parent, author, committer
+		 * information followed by "\n\n".
+		 */
+		p = strstr(msg.message, "\n\n");
+		if (p) {
+			p += 2;
+			strbuf_addstr(&msgbuf, p);
+		}
+
+		if (opts->record_origin) {
 			strbuf_addstr(&msgbuf, "(cherry picked from commit ");
 			strbuf_addstr(&msgbuf, sha1_to_hex(commit->object.sha1));
 			strbuf_addstr(&msgbuf, ")\n");
 		}
-		if (!no_commit)
-			write_cherry_pick_head();
+		if (!opts->no_commit)
+			write_cherry_pick_head(commit);
 	}
 
-	if (!strategy || !strcmp(strategy, "recursive") || action == REVERT) {
+	if (!opts->strategy || !strcmp(opts->strategy, "recursive") || opts->action == REVERT) {
 		res = do_recursive_merge(base, next, base_label, next_label,
-					 head, &msgbuf);
+					 head, &msgbuf, opts);
 		write_message(&msgbuf, defmsg);
 	} else {
 		struct commit_list *common = NULL;
@@ -492,23 +582,23 @@ static int do_pick_commit(void)
 
 		commit_list_insert(base, &common);
 		commit_list_insert(next, &remotes);
-		res = try_merge_command(strategy, xopts_nr, xopts, common,
-					sha1_to_hex(head), remotes);
+		res = try_merge_command(opts->strategy, opts->xopts_nr, opts->xopts,
+					common, sha1_to_hex(head), remotes);
 		free_commit_list(common);
 		free_commit_list(remotes);
 	}
 
 	if (res) {
-		error(action == REVERT
+		error(opts->action == REVERT
 		      ? _("could not revert %s... %s")
 		      : _("could not apply %s... %s"),
 		      find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV),
 		      msg.subject);
 		print_advice();
-		rerere(allow_rerere_auto);
+		rerere(opts->allow_rerere_auto);
 	} else {
-		if (!no_commit)
-			res = run_git_commit(defmsg);
+		if (!opts->no_commit)
+			res = run_git_commit(defmsg, opts);
 	}
 
 	free_message(&msg);
@@ -517,18 +607,18 @@ static int do_pick_commit(void)
 	return res;
 }
 
-static void prepare_revs(struct rev_info *revs)
+static void prepare_revs(struct rev_info *revs, struct replay_opts *opts)
 {
 	int argc;
 
 	init_revisions(revs, NULL);
 	revs->no_walk = 1;
-	if (action != REVERT)
+	if (opts->action != REVERT)
 		revs->reverse = 1;
 
-	argc = setup_revisions(commit_argc, commit_argv, revs, NULL);
+	argc = setup_revisions(opts->commit_argc, opts->commit_argv, revs, NULL);
 	if (argc > 1)
-		usage(*revert_or_cherry_pick_usage());
+		usage(*revert_or_cherry_pick_usage(opts));
 
 	if (prepare_revision_walk(revs))
 		die(_("revision walk setup failed"));
@@ -537,64 +627,403 @@ static void prepare_revs(struct rev_info *revs)
 		die(_("empty commit set passed"));
 }
 
-static void read_and_refresh_cache(const char *me)
+static void read_and_refresh_cache(struct replay_opts *opts)
 {
 	static struct lock_file index_lock;
 	int index_fd = hold_locked_index(&index_lock, 0);
 	if (read_index_preload(&the_index, NULL) < 0)
-		die(_("git %s: failed to read the index"), me);
+		die(_("git %s: failed to read the index"), action_name(opts));
 	refresh_index(&the_index, REFRESH_QUIET|REFRESH_UNMERGED, NULL, NULL, NULL);
 	if (the_index.cache_changed) {
 		if (write_index(&the_index, index_fd) ||
 		    commit_locked_index(&index_lock))
-			die(_("git %s: failed to refresh the index"), me);
+			die(_("git %s: failed to refresh the index"), action_name(opts));
 	}
 	rollback_lock_file(&index_lock);
 }
 
-static int revert_or_cherry_pick(int argc, const char **argv)
+/*
+ * Append a commit to the end of the commit_list.
+ *
+ * next starts by pointing to the variable that holds the head of an
+ * empty commit_list, and is updated to point to the "next" field of
+ * the last item on the list as new commits are appended.
+ *
+ * Usage example:
+ *
+ *     struct commit_list *list;
+ *     struct commit_list **next = &list;
+ *
+ *     next = commit_list_append(c1, next);
+ *     next = commit_list_append(c2, next);
+ *     assert(commit_list_count(list) == 2);
+ *     return list;
+ */
+static struct commit_list **commit_list_append(struct commit *commit,
+					       struct commit_list **next)
+{
+	struct commit_list *new = xmalloc(sizeof(struct commit_list));
+	new->item = commit;
+	*next = new;
+	new->next = NULL;
+	return &new->next;
+}
+
+static int format_todo(struct strbuf *buf, struct commit_list *todo_list,
+		struct replay_opts *opts)
+{
+	struct commit_list *cur = NULL;
+	struct commit_message msg = { NULL, NULL, NULL, NULL, NULL };
+	const char *sha1_abbrev = NULL;
+	const char *action_str = opts->action == REVERT ? "revert" : "pick";
+
+	for (cur = todo_list; cur; cur = cur->next) {
+		sha1_abbrev = find_unique_abbrev(cur->item->object.sha1, DEFAULT_ABBREV);
+		if (get_message(cur->item, &msg))
+			return error(_("Cannot get commit message for %s"), sha1_abbrev);
+		strbuf_addf(buf, "%s %s %s\n", action_str, sha1_abbrev, msg.subject);
+	}
+	return 0;
+}
+
+static struct commit *parse_insn_line(char *start, struct replay_opts *opts)
+{
+	unsigned char commit_sha1[20];
+	char sha1_abbrev[40];
+	enum replay_action action;
+	int insn_len = 0;
+	char *p, *q;
+
+	if (!prefixcmp(start, "pick ")) {
+		action = CHERRY_PICK;
+		insn_len = strlen("pick");
+		p = start + insn_len + 1;
+	} else if (!prefixcmp(start, "revert ")) {
+		action = REVERT;
+		insn_len = strlen("revert");
+		p = start + insn_len + 1;
+	} else
+		return NULL;
+
+	q = strchr(p, ' ');
+	if (!q)
+		return NULL;
+	q++;
+
+	strlcpy(sha1_abbrev, p, q - p);
+
+	/*
+	 * Verify that the action matches up with the one in
+	 * opts; we don't support arbitrary instructions
+	 */
+	if (action != opts->action) {
+		const char *action_str;
+		action_str = action == REVERT ? "revert" : "cherry-pick";
+		error(_("Cannot %s during a %s"), action_str, action_name(opts));
+		return NULL;
+	}
+
+	if (get_sha1(sha1_abbrev, commit_sha1) < 0)
+		return NULL;
+
+	return lookup_commit_reference(commit_sha1);
+}
+
+static int parse_insn_buffer(char *buf, struct commit_list **todo_list,
+			struct replay_opts *opts)
+{
+	struct commit_list **next = todo_list;
+	struct commit *commit;
+	char *p = buf;
+	int i;
+
+	for (i = 1; *p; i++) {
+		commit = parse_insn_line(p, opts);
+		if (!commit)
+			return error(_("Could not parse line %d."), i);
+		next = commit_list_append(commit, next);
+		p = strchrnul(p, '\n');
+		if (*p)
+			p++;
+	}
+	if (!*todo_list)
+		return error(_("No commits parsed."));
+	return 0;
+}
+
+static void read_populate_todo(struct commit_list **todo_list,
+			struct replay_opts *opts)
+{
+	const char *todo_file = git_path(SEQ_TODO_FILE);
+	struct strbuf buf = STRBUF_INIT;
+	int fd, res;
+
+	fd = open(todo_file, O_RDONLY);
+	if (fd < 0)
+		die_errno(_("Could not open %s."), todo_file);
+	if (strbuf_read(&buf, fd, 0) < 0) {
+		close(fd);
+		strbuf_release(&buf);
+		die(_("Could not read %s."), todo_file);
+	}
+	close(fd);
+
+	res = parse_insn_buffer(buf.buf, todo_list, opts);
+	strbuf_release(&buf);
+	if (res)
+		die(_("Unusable instruction sheet: %s"), todo_file);
+}
+
+static int populate_opts_cb(const char *key, const char *value, void *data)
+{
+	struct replay_opts *opts = data;
+	int error_flag = 1;
+
+	if (!value)
+		error_flag = 0;
+	else if (!strcmp(key, "options.no-commit"))
+		opts->no_commit = git_config_bool_or_int(key, value, &error_flag);
+	else if (!strcmp(key, "options.edit"))
+		opts->edit = git_config_bool_or_int(key, value, &error_flag);
+	else if (!strcmp(key, "options.signoff"))
+		opts->signoff = git_config_bool_or_int(key, value, &error_flag);
+	else if (!strcmp(key, "options.record-origin"))
+		opts->record_origin = git_config_bool_or_int(key, value, &error_flag);
+	else if (!strcmp(key, "options.allow-ff"))
+		opts->allow_ff = git_config_bool_or_int(key, value, &error_flag);
+	else if (!strcmp(key, "options.mainline"))
+		opts->mainline = git_config_int(key, value);
+	else if (!strcmp(key, "options.strategy"))
+		git_config_string(&opts->strategy, key, value);
+	else if (!strcmp(key, "options.strategy-option")) {
+		ALLOC_GROW(opts->xopts, opts->xopts_nr + 1, opts->xopts_alloc);
+		opts->xopts[opts->xopts_nr++] = xstrdup(value);
+	} else
+		return error(_("Invalid key: %s"), key);
+
+	if (!error_flag)
+		return error(_("Invalid value for %s: %s"), key, value);
+
+	return 0;
+}
+
+static void read_populate_opts(struct replay_opts **opts_ptr)
+{
+	const char *opts_file = git_path(SEQ_OPTS_FILE);
+
+	if (!file_exists(opts_file))
+		return;
+	if (git_config_from_file(populate_opts_cb, opts_file, *opts_ptr) < 0)
+		die(_("Malformed options sheet: %s"), opts_file);
+}
+
+static void walk_revs_populate_todo(struct commit_list **todo_list,
+				struct replay_opts *opts)
 {
 	struct rev_info revs;
+	struct commit *commit;
+	struct commit_list **next;
 
-	git_config(git_default_config, NULL);
-	me = action == REVERT ? "revert" : "cherry-pick";
-	setenv(GIT_REFLOG_ACTION, me, 0);
-	parse_args(argc, argv);
-
-	if (allow_ff) {
-		if (signoff)
-			die(_("cherry-pick --ff cannot be used with --signoff"));
-		if (no_commit)
-			die(_("cherry-pick --ff cannot be used with --no-commit"));
-		if (no_replay)
-			die(_("cherry-pick --ff cannot be used with -x"));
-		if (edit)
-			die(_("cherry-pick --ff cannot be used with --edit"));
+	prepare_revs(&revs, opts);
+
+	next = todo_list;
+	while ((commit = get_revision(&revs)))
+		next = commit_list_append(commit, next);
+}
+
+static int create_seq_dir(void)
+{
+	const char *seq_dir = git_path(SEQ_DIR);
+
+	if (file_exists(seq_dir))
+		return error(_("%s already exists."), seq_dir);
+	else if (mkdir(seq_dir, 0777) < 0)
+		die_errno(_("Could not create sequencer directory '%s'."), seq_dir);
+	return 0;
+}
+
+static void save_head(const char *head)
+{
+	const char *head_file = git_path(SEQ_HEAD_FILE);
+	static struct lock_file head_lock;
+	struct strbuf buf = STRBUF_INIT;
+	int fd;
+
+	fd = hold_lock_file_for_update(&head_lock, head_file, LOCK_DIE_ON_ERROR);
+	strbuf_addf(&buf, "%s\n", head);
+	if (write_in_full(fd, buf.buf, buf.len) < 0)
+		die_errno(_("Could not write to %s."), head_file);
+	if (commit_lock_file(&head_lock) < 0)
+		die(_("Error wrapping up %s."), head_file);
+}
+
+static void save_todo(struct commit_list *todo_list, struct replay_opts *opts)
+{
+	const char *todo_file = git_path(SEQ_TODO_FILE);
+	static struct lock_file todo_lock;
+	struct strbuf buf = STRBUF_INIT;
+	int fd;
+
+	fd = hold_lock_file_for_update(&todo_lock, todo_file, LOCK_DIE_ON_ERROR);
+	if (format_todo(&buf, todo_list, opts) < 0)
+		die(_("Could not format %s."), todo_file);
+	if (write_in_full(fd, buf.buf, buf.len) < 0) {
+		strbuf_release(&buf);
+		die_errno(_("Could not write to %s."), todo_file);
+	}
+	if (commit_lock_file(&todo_lock) < 0) {
+		strbuf_release(&buf);
+		die(_("Error wrapping up %s."), todo_file);
 	}
+	strbuf_release(&buf);
+}
 
-	read_and_refresh_cache(me);
+static void save_opts(struct replay_opts *opts)
+{
+	const char *opts_file = git_path(SEQ_OPTS_FILE);
+
+	if (opts->no_commit)
+		git_config_set_in_file(opts_file, "options.no-commit", "true");
+	if (opts->edit)
+		git_config_set_in_file(opts_file, "options.edit", "true");
+	if (opts->signoff)
+		git_config_set_in_file(opts_file, "options.signoff", "true");
+	if (opts->record_origin)
+		git_config_set_in_file(opts_file, "options.record-origin", "true");
+	if (opts->allow_ff)
+		git_config_set_in_file(opts_file, "options.allow-ff", "true");
+	if (opts->mainline) {
+		struct strbuf buf = STRBUF_INIT;
+		strbuf_addf(&buf, "%d", opts->mainline);
+		git_config_set_in_file(opts_file, "options.mainline", buf.buf);
+		strbuf_release(&buf);
+	}
+	if (opts->strategy)
+		git_config_set_in_file(opts_file, "options.strategy", opts->strategy);
+	if (opts->xopts) {
+		int i;
+		for (i = 0; i < opts->xopts_nr; i++)
+			git_config_set_multivar_in_file(opts_file,
+							"options.strategy-option",
+							opts->xopts[i], "^$", 0);
+	}
+}
 
-	prepare_revs(&revs);
+static int pick_commits(struct commit_list *todo_list, struct replay_opts *opts)
+{
+	struct commit_list *cur;
+	int res;
 
-	while ((commit = get_revision(&revs))) {
-		int res = do_pick_commit();
-		if (res)
+	setenv(GIT_REFLOG_ACTION, action_name(opts), 0);
+	if (opts->allow_ff)
+		assert(!(opts->signoff || opts->no_commit ||
+				opts->record_origin || opts->edit));
+	read_and_refresh_cache(opts);
+
+	for (cur = todo_list; cur; cur = cur->next) {
+		save_todo(cur, opts);
+		res = do_pick_commit(cur->item, opts);
+		if (res) {
+			if (!cur->next)
+				/*
+				 * An error was encountered while
+				 * picking the last commit; the
+				 * sequencer state is useless now --
+				 * the user simply needs to resolve
+				 * the conflict and commit
+				 */
+				remove_sequencer_state(0);
 			return res;
+		}
 	}
 
+	/*
+	 * Sequence of picks finished successfully; cleanup by
+	 * removing the .git/sequencer directory
+	 */
+	remove_sequencer_state(1);
 	return 0;
 }
 
+static int pick_revisions(struct replay_opts *opts)
+{
+	struct commit_list *todo_list = NULL;
+	unsigned char sha1[20];
+
+	read_and_refresh_cache(opts);
+
+	/*
+	 * Decide what to do depending on the arguments; a fresh
+	 * cherry-pick should be handled differently from an existing
+	 * one that is being continued
+	 */
+	if (opts->subcommand == REPLAY_RESET) {
+		remove_sequencer_state(1);
+		return 0;
+	} else if (opts->subcommand == REPLAY_CONTINUE) {
+		if (!file_exists(git_path(SEQ_TODO_FILE)))
+			goto error;
+		read_populate_opts(&opts);
+		read_populate_todo(&todo_list, opts);
+
+		/* Verify that the conflict has been resolved */
+		if (!index_differs_from("HEAD", 0))
+			todo_list = todo_list->next;
+	} else {
+		/*
+		 * Start a new cherry-pick/ revert sequence; but
+		 * first, make sure that an existing one isn't in
+		 * progress
+		 */
+
+		walk_revs_populate_todo(&todo_list, opts);
+		if (create_seq_dir() < 0) {
+			error(_("A cherry-pick or revert is in progress."));
+			advise(_("Use --continue to continue the operation"));
+			advise(_("or --reset to forget about it"));
+			return -1;
+		}
+		if (get_sha1("HEAD", sha1)) {
+			if (opts->action == REVERT)
+				return error(_("Can't revert as initial commit"));
+			return error(_("Can't cherry-pick into empty head"));
+		}
+		save_head(sha1_to_hex(sha1));
+		save_opts(opts);
+	}
+	return pick_commits(todo_list, opts);
+error:
+	return error(_("No %s in progress"), action_name(opts));
+}
+
 int cmd_revert(int argc, const char **argv, const char *prefix)
 {
+	struct replay_opts opts;
+	int res;
+
+	memset(&opts, 0, sizeof(opts));
 	if (isatty(0))
-		edit = 1;
-	action = REVERT;
-	return revert_or_cherry_pick(argc, argv);
+		opts.edit = 1;
+	opts.action = REVERT;
+	git_config(git_default_config, NULL);
+	parse_args(argc, argv, &opts);
+	res = pick_revisions(&opts);
+	if (res < 0)
+		die(_("revert failed"));
+	return res;
 }
 
 int cmd_cherry_pick(int argc, const char **argv, const char *prefix)
 {
-	action = CHERRY_PICK;
-	return revert_or_cherry_pick(argc, argv);
+	struct replay_opts opts;
+	int res;
+
+	memset(&opts, 0, sizeof(opts));
+	opts.action = CHERRY_PICK;
+	git_config(git_default_config, NULL);
+	parse_args(argc, argv, &opts);
+	res = pick_revisions(&opts);
+	if (res < 0)
+		die(_("cherry-pick failed"));
+	return res;
 }