builtin rebase actions

index b2ddfa8dbf..10da4c978b 100644
@@ -91,6 +91,7 @@ struct rebase_options {
 		REBASE_INTERACTIVE_EXPLICIT = 1<<4,
 	} flags;
 	struct strbuf git_am_opt;
+	const char *action;
 };
 
 static int is_interactive(struct rebase_options *opts)

@@ -115,6 +116,62 @@ static const char *state_dir_path(const char *filename, struct rebase_options *o
 	return path.buf;
 }
 
+/* Read one file, then strip line endings */
+static int read_one(const char *path, struct strbuf *buf)
+{
+	if (strbuf_read_file(buf, path, 0) < 0)
+		return error_errno(_("could not read '%s'"), path);
+	strbuf_trim_trailing_newline(buf);
+	return 0;
+}
+
+/* Initialize the rebase options from the state directory. */
+static int read_basic_state(struct rebase_options *opts)
+{
+	struct strbuf head_name = STRBUF_INIT;
+	struct strbuf buf = STRBUF_INIT;
+	struct object_id oid;
+
+	if (read_one(state_dir_path("head-name", opts), &head_name) ||
+	    read_one(state_dir_path("onto", opts), &buf))
+		return -1;
+	opts->head_name = starts_with(head_name.buf, "refs/") ?
+		xstrdup(head_name.buf) : NULL;
+	strbuf_release(&head_name);
+	if (get_oid(buf.buf, &oid))
+		return error(_("could not get 'onto': '%s'"), buf.buf);
+	opts->onto = lookup_commit_or_die(&oid, buf.buf);
+
+	/*
+	 * We always write to orig-head, but interactive rebase used to write to
+	 * head. Fall back to reading from head to cover for the case that the
+	 * user upgraded git with an ongoing interactive rebase.
+	 */
+	strbuf_reset(&buf);
+	if (file_exists(state_dir_path("orig-head", opts))) {
+		if (read_one(state_dir_path("orig-head", opts), &buf))
+			return -1;
+	} else if (read_one(state_dir_path("head", opts), &buf))
+		return -1;
+	if (get_oid(buf.buf, &opts->orig_head))
+		return error(_("invalid orig-head: '%s'"), buf.buf);
+
+	strbuf_reset(&buf);
+	if (read_one(state_dir_path("quiet", opts), &buf))
+		return -1;
+	if (buf.len)
+		opts->flags &= ~REBASE_NO_QUIET;
+	else
+		opts->flags |= REBASE_NO_QUIET;
+
+	if (file_exists(state_dir_path("verbose", opts)))
+		opts->flags |= REBASE_VERBOSE;
+
+	strbuf_release(&buf);
+
+	return 0;
+}
+
 static int finish_rebase(struct rebase_options *opts)
 {
 	struct strbuf dir = STRBUF_INIT;

@@ -168,12 +225,13 @@ static int run_specific_rebase(struct rebase_options *opts)
 	add_var(&script_snippet, "state_dir", opts->state_dir);
 
 	add_var(&script_snippet, "upstream_name", opts->upstream_name);
-	add_var(&script_snippet, "upstream",
-				 oid_to_hex(&opts->upstream->object.oid));
+	add_var(&script_snippet, "upstream", opts->upstream ?
+		oid_to_hex(&opts->upstream->object.oid) : NULL);
 	add_var(&script_snippet, "head_name",
 		opts->head_name ? opts->head_name : "detached HEAD");
 	add_var(&script_snippet, "orig_head", oid_to_hex(&opts->orig_head));
-	add_var(&script_snippet, "onto", oid_to_hex(&opts->onto->object.oid));
+	add_var(&script_snippet, "onto", opts->onto ?
+		oid_to_hex(&opts->onto->object.oid) : NULL);
 	add_var(&script_snippet, "onto_name", opts->onto_name);
 	add_var(&script_snippet, "revisions", opts->revisions);
 	add_var(&script_snippet, "restrict_revision", opts->restrict_revision ?

@@ -189,6 +247,7 @@ static int run_specific_rebase(struct rebase_options *opts)
 		opts->flags & REBASE_FORCE ? "t" : "");
 	if (opts->switch_to)
 		add_var(&script_snippet, "switch_to", opts->switch_to);
+	add_var(&script_snippet, "action", opts->action ? opts->action : "");
 
 	switch (opts->type) {
 	case REBASE_AM:

@@ -400,12 +459,16 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		.git_am_opt = STRBUF_INIT,
 	};
 	const char *branch_name;
-	int ret, flags, in_progress = 0;
+	int ret, flags, total_argc, in_progress = 0;
 	int ok_to_skip_pre_rebase = 0;
 	struct strbuf msg = STRBUF_INIT;
 	struct strbuf revisions = STRBUF_INIT;
 	struct strbuf buf = STRBUF_INIT;
 	struct object_id merge_base;
+	enum {
+		NO_ACTION,
+		ACTION_CONTINUE,
+	} action = NO_ACTION;
 	struct option builtin_rebase_options[] = {
 		OPT_STRING(0, "onto", &options.onto_name,
 			   N_("revision"),

@@ -427,6 +490,8 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		OPT_BIT(0, "no-ff", &options.flags,
 			N_("cherry-pick all commits, even if unchanged"),
 			REBASE_FORCE),
+		OPT_CMDMODE(0, "continue", &action, N_("continue"),
+			    ACTION_CONTINUE),
 		OPT_END(),
 	};
 

@@ -480,14 +545,55 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 	if (options.type != REBASE_UNSPECIFIED)
 		in_progress = 1;
 
+	total_argc = argc;
 	argc = parse_options(argc, argv, prefix,
 			     builtin_rebase_options,
 			     builtin_rebase_usage, 0);
 
+	if (action != NO_ACTION && total_argc != 2) {
+		usage_with_options(builtin_rebase_usage,
+				   builtin_rebase_options);
+	}
+
 	if (argc > 2)
 		usage_with_options(builtin_rebase_usage,
 				   builtin_rebase_options);
 
+	switch (action) {
+	case ACTION_CONTINUE: {
+		struct object_id head;
+		struct lock_file lock_file = LOCK_INIT;
+		int fd;
+
+		options.action = "continue";
+
+		/* Sanity check */
+		if (get_oid("HEAD", &head))
+			die(_("Cannot read HEAD"));
+
+		fd = hold_locked_index(&lock_file, 0);
+		if (read_index(the_repository->index) < 0)
+			die(_("could not read index"));
+		refresh_index(the_repository->index, REFRESH_QUIET, NULL, NULL,
+			      NULL);
+		if (0 <= fd)
+			update_index_if_able(the_repository->index,
+					     &lock_file);
+		rollback_lock_file(&lock_file);
+
+		if (has_unstaged_changes(1)) {
+			puts(_("You must edit all merge conflicts and then\n"
+			       "mark them as resolved using git add"));
+			exit(1);
+		}
+		if (read_basic_state(&options))
+			exit(1);
+		goto run_rebase;
+	}
+	default:
+		die("TODO");
+	}
+
 	/* Make sure no rebase is in progress */
 	if (in_progress) {
 		const char *last_slash = strrchr(options.state_dir, '/');

@@ -719,6 +825,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 
 	options.revisions = revisions.buf;
 
+run_rebase:
 	ret = !!run_specific_rebase(&options);
 
 cleanup:

index 030556111d..fdc0ffbafb 100644
@@ -120,6 +120,15 @@ void strbuf_trim_trailing_dir_sep(struct strbuf *sb)
 	sb->buf[sb->len] = '\0';
 }
 
+void strbuf_trim_trailing_newline(struct strbuf *sb)
+{
+	if (sb->len > 0 && sb->buf[sb->len - 1] == '\n') {
+		if (--sb->len > 0 && sb->buf[sb->len - 1] == '\r')
+			--sb->len;
+		sb->buf[sb->len] = '\0';
+	}
+}
+
 void strbuf_ltrim(struct strbuf *sb)
 {
 	char *b = sb->buf;

index 60a35aef16..b7aea8a966 100644
@@ -190,6 +190,9 @@ extern void strbuf_ltrim(struct strbuf *);
 /* Strip trailing directory separators */
 extern void strbuf_trim_trailing_dir_sep(struct strbuf *);
 
+/* Strip trailing LF or CR/LF */
+extern void strbuf_trim_trailing_newline(struct strbuf *sb);
+
 /**
  * Replace the contents of the strbuf with a reencoded form.  Returns -1
  * on error, 0 on success.

index 10da4c978b..7a903838b1 100644
@@ -21,6 +21,7 @@
 #include "diff.h"
 #include "wt-status.h"
 #include "revision.h"
+#include "rerere.h"
 
 static char const * const builtin_rebase_usage[] = {
 	N_("git rebase [-i] [options] [--exec <cmd>] [--onto <newbase>] "

@@ -468,6 +469,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 	enum {
 		NO_ACTION,
 		ACTION_CONTINUE,
+		ACTION_SKIP,
 	} action = NO_ACTION;
 	struct option builtin_rebase_options[] = {
 		OPT_STRING(0, "onto", &options.onto_name,

@@ -492,6 +494,8 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 			REBASE_FORCE),
 		OPT_CMDMODE(0, "continue", &action, N_("continue"),
 			    ACTION_CONTINUE),
+		OPT_CMDMODE(0, "skip", &action,
+			    N_("skip current patch and continue"), ACTION_SKIP),
 		OPT_END(),
 	};
 

@@ -590,6 +594,20 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 			exit(1);
 		goto run_rebase;
 	}
+	case ACTION_SKIP: {
+		struct string_list merge_rr = STRING_LIST_INIT_DUP;
+
+		options.action = "skip";
+
+		rerere_clear(&merge_rr);
+		string_list_clear(&merge_rr, 1);
+
+		if (reset_head(NULL, "reset", NULL, 0) < 0)
+			die(_("could not discard worktree changes"));
+		if (read_basic_state(&options))
+			exit(1);
+		goto run_rebase;
+	}
 	default:
 		die("TODO");
 	}

index 7a903838b1..8e94f6cc85 100644
@@ -470,6 +470,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		NO_ACTION,
 		ACTION_CONTINUE,
 		ACTION_SKIP,
+		ACTION_ABORT,
 	} action = NO_ACTION;
 	struct option builtin_rebase_options[] = {
 		OPT_STRING(0, "onto", &options.onto_name,

@@ -496,6 +497,9 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 			    ACTION_CONTINUE),
 		OPT_CMDMODE(0, "skip", &action,
 			    N_("skip current patch and continue"), ACTION_SKIP),
+		OPT_CMDMODE(0, "abort", &action,
+			    N_("abort and check out the original branch"),
+			    ACTION_ABORT),
 		OPT_END(),
 	};
 

@@ -608,6 +612,22 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 			exit(1);
 		goto run_rebase;
 	}
+	case ACTION_ABORT: {
+		struct string_list merge_rr = STRING_LIST_INIT_DUP;
+		options.action = "abort";
+
+		rerere_clear(&merge_rr);
+		string_list_clear(&merge_rr, 1);
+
+		if (read_basic_state(&options))
+			exit(1);
+		if (reset_head(&options.orig_head, "reset",
+			       options.head_name, 0) < 0)
+			die(_("could not move back to %s"),
+			    oid_to_hex(&options.orig_head));
+		ret = finish_rebase(&options);
+		goto cleanup;
+	}
 	default:
 		die("TODO");
 	}

index 8e94f6cc85..0d805480a1 100644
@@ -471,6 +471,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		ACTION_CONTINUE,
 		ACTION_SKIP,
 		ACTION_ABORT,
+		ACTION_QUIT,
 	} action = NO_ACTION;
 	struct option builtin_rebase_options[] = {
 		OPT_STRING(0, "onto", &options.onto_name,

@@ -500,6 +501,8 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		OPT_CMDMODE(0, "abort", &action,
 			    N_("abort and check out the original branch"),
 			    ACTION_ABORT),
+		OPT_CMDMODE(0, "quit", &action,
+			    N_("abort but keep HEAD where it is"), ACTION_QUIT),
 		OPT_END(),
 	};
 

@@ -628,6 +631,14 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		ret = finish_rebase(&options);
 		goto cleanup;
 	}
+	case ACTION_QUIT: {
+		strbuf_reset(&buf);
+		strbuf_addstr(&buf, options.state_dir);
+		ret = !!remove_dir_recursively(&buf, 0);
+		if (ret)
+			die(_("could not remove '%s'"), options.state_dir);
+		goto cleanup;
+	}
 	default:
 		die("TODO");
 	}

index 0d805480a1..e3dd2f511e 100644
@@ -472,6 +472,8 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		ACTION_SKIP,
 		ACTION_ABORT,
 		ACTION_QUIT,
+		ACTION_EDIT_TODO,
+		ACTION_SHOW_CURRENT_PATCH,
 	} action = NO_ACTION;
 	struct option builtin_rebase_options[] = {
 		OPT_STRING(0, "onto", &options.onto_name,

@@ -503,6 +505,11 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 			    ACTION_ABORT),
 		OPT_CMDMODE(0, "quit", &action,
 			    N_("abort but keep HEAD where it is"), ACTION_QUIT),
+		OPT_CMDMODE(0, "edit-todo", &action, N_("edit the todo list "
+			    "during an interactive rebase"), ACTION_EDIT_TODO),
+		OPT_CMDMODE(0, "show-current-patch", &action,
+			    N_("show the patch file being applied or merged"),
+			    ACTION_SHOW_CURRENT_PATCH),
 		OPT_END(),
 	};
 

@@ -570,6 +577,10 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		usage_with_options(builtin_rebase_usage,
 				   builtin_rebase_options);
 
+	if (action == ACTION_EDIT_TODO && !is_interactive(&options))
+		die(_("The --edit-todo action can only be used during "
+		      "interactive rebase."));
+
 	switch (action) {
 	case ACTION_CONTINUE: {
 		struct object_id head;

@@ -639,8 +650,18 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 			die(_("could not remove '%s'"), options.state_dir);
 		goto cleanup;
 	}
+	case ACTION_EDIT_TODO:
+		options.action = "edit-todo";
+		options.dont_finish_rebase = 1;
+		goto run_rebase;
+	case ACTION_SHOW_CURRENT_PATCH:
+		options.action = "show-current-patch";
+		options.dont_finish_rebase = 1;
+		goto run_rebase;
+	case NO_ACTION:
+		break;
 	default:
-		die("TODO");
+		BUG("action: %d", action);
 	}
 
 	/* Make sure no rebase is in progress */

index e3dd2f511e..1344e071f3 100644
@@ -577,6 +577,9 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		usage_with_options(builtin_rebase_usage,
 				   builtin_rebase_options);
 
+	if (action != NO_ACTION && !in_progress)
+		die(_("No rebase in progress?"));
+
 	if (action == ACTION_EDIT_TODO && !is_interactive(&options))
 		die(_("The --edit-todo action can only be used during "
 		      "interactive rebase."));

index 1344e071f3..75c4ac66e0 100644
@@ -539,6 +539,11 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 
 	git_config(rebase_config, &options);
 
+	strbuf_reset(&buf);
+	strbuf_addf(&buf, "%s/applying", apply_dir());
+	if(file_exists(buf.buf))
+		die(_("It looks like 'git am' is in progress. Cannot rebase."));
+
 	if (is_directory(apply_dir())) {
 		options.type = REBASE_AM;
 		options.state_dir = apply_dir();