1 files changed, 325 insertions, 52 deletions

diff --git a/builtin/replace.c b/builtin/replace.c
index b62420a01a..85d39b58d8 100644
--- a/builtin/replace.c
+++ b/builtin/replace.c
@@ -12,18 +12,22 @@
 #include "builtin.h"
 #include "refs.h"
 #include "parse-options.h"
+#include "run-command.h"
+#include "tag.h"
 
 static const char * const git_replace_usage[] = {
 	N_("git replace [-f] <object> <replacement>"),
+	N_("git replace [-f] --edit <object>"),
+	N_("git replace [-f] --graft <commit> [<parent>...]"),
 	N_("git replace -d <object>..."),
 	N_("git replace [--format=<format>] [-l [<pattern>]]"),
 	NULL
 };
 
 enum replace_format {
-      REPLACE_FORMAT_SHORT,
-      REPLACE_FORMAT_MEDIUM,
-      REPLACE_FORMAT_LONG
+	REPLACE_FORMAT_SHORT,
+	REPLACE_FORMAT_MEDIUM,
+	REPLACE_FORMAT_LONG
 };
 
 struct show_data {
@@ -123,26 +127,37 @@ static int delete_replace_ref(const char *name, const char *ref,
 	return 0;
 }
 
-static int replace_object(const char *object_ref, const char *replace_ref,
-			  int force)
+static void check_ref_valid(unsigned char object[20],
+			    unsigned char prev[20],
+			    char *ref,
+			    int ref_size,
+			    int force)
 {
-	unsigned char object[20], prev[20], repl[20];
-	enum object_type obj_type, repl_type;
-	char ref[PATH_MAX];
-	struct ref_lock *lock;
-
-	if (get_sha1(object_ref, object))
-		die("Failed to resolve '%s' as a valid ref.", object_ref);
-	if (get_sha1(replace_ref, repl))
-		die("Failed to resolve '%s' as a valid ref.", replace_ref);
-
-	if (snprintf(ref, sizeof(ref),
+	if (snprintf(ref, ref_size,
 		     "refs/replace/%s",
-		     sha1_to_hex(object)) > sizeof(ref) - 1)
+		     sha1_to_hex(object)) > ref_size - 1)
 		die("replace ref name too long: %.*s...", 50, ref);
 	if (check_refname_format(ref, 0))
 		die("'%s' is not a valid ref name.", ref);
 
+	if (read_ref(ref, prev))
+		hashclr(prev);
+	else if (!force)
+		die("replace ref '%s' already exists", ref);
+}
+
+static int replace_object_sha1(const char *object_ref,
+			       unsigned char object[20],
+			       const char *replace_ref,
+			       unsigned char repl[20],
+			       int force)
+{
+	unsigned char prev[20];
+	enum object_type obj_type, repl_type;
+	char ref[PATH_MAX];
+	struct ref_transaction *transaction;
+	struct strbuf err = STRBUF_INIT;
+
 	obj_type = sha1_object_info(object, NULL);
 	repl_type = sha1_object_info(repl, NULL);
 	if (!force && obj_type != repl_type)
@@ -152,28 +167,274 @@ static int replace_object(const char *object_ref, const char *replace_ref,
 		    object_ref, typename(obj_type),
 		    replace_ref, typename(repl_type));
 
-	if (read_ref(ref, prev))
-		hashclr(prev);
-	else if (!force)
-		die("replace ref '%s' already exists", ref);
+	check_ref_valid(object, prev, ref, sizeof(ref), force);
 
-	lock = lock_any_ref_for_update(ref, prev, 0, NULL);
-	if (!lock)
-		die("%s: cannot lock the ref", ref);
-	if (write_ref_sha1(lock, repl, NULL) < 0)
-		die("%s: cannot update the ref", ref);
+	transaction = ref_transaction_begin(&err);
+	if (!transaction ||
+	    ref_transaction_update(transaction, ref, repl, prev,
+				   0, 1, NULL, &err) ||
+	    ref_transaction_commit(transaction, &err))
+		die("%s", err.buf);
 
+	ref_transaction_free(transaction);
 	return 0;
 }
 
+static int replace_object(const char *object_ref, const char *replace_ref, int force)
+{
+	unsigned char object[20], repl[20];
+
+	if (get_sha1(object_ref, object))
+		die("Failed to resolve '%s' as a valid ref.", object_ref);
+	if (get_sha1(replace_ref, repl))
+		die("Failed to resolve '%s' as a valid ref.", replace_ref);
+
+	return replace_object_sha1(object_ref, object, replace_ref, repl, force);
+}
+
+/*
+ * Write the contents of the object named by "sha1" to the file "filename".
+ * If "raw" is true, then the object's raw contents are printed according to
+ * "type". Otherwise, we pretty-print the contents for human editing.
+ */
+static void export_object(const unsigned char *sha1, enum object_type type,
+			  int raw, const char *filename)
+{
+	struct child_process cmd = CHILD_PROCESS_INIT;
+	int fd;
+
+	fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
+	if (fd < 0)
+		die_errno("unable to open %s for writing", filename);
+
+	argv_array_push(&cmd.args, "--no-replace-objects");
+	argv_array_push(&cmd.args, "cat-file");
+	if (raw)
+		argv_array_push(&cmd.args, typename(type));
+	else
+		argv_array_push(&cmd.args, "-p");
+	argv_array_push(&cmd.args, sha1_to_hex(sha1));
+	cmd.git_cmd = 1;
+	cmd.out = fd;
+
+	if (run_command(&cmd))
+		die("cat-file reported failure");
+}
+
+/*
+ * Read a previously-exported (and possibly edited) object back from "filename",
+ * interpreting it as "type", and writing the result to the object database.
+ * The sha1 of the written object is returned via sha1.
+ */
+static void import_object(unsigned char *sha1, enum object_type type,
+			  int raw, const char *filename)
+{
+	int fd;
+
+	fd = open(filename, O_RDONLY);
+	if (fd < 0)
+		die_errno("unable to open %s for reading", filename);
+
+	if (!raw && type == OBJ_TREE) {
+		const char *argv[] = { "mktree", NULL };
+		struct child_process cmd = CHILD_PROCESS_INIT;
+		struct strbuf result = STRBUF_INIT;
+
+		cmd.argv = argv;
+		cmd.git_cmd = 1;
+		cmd.in = fd;
+		cmd.out = -1;
+
+		if (start_command(&cmd))
+			die("unable to spawn mktree");
+
+		if (strbuf_read(&result, cmd.out, 41) < 0)
+			die_errno("unable to read from mktree");
+		close(cmd.out);
+
+		if (finish_command(&cmd))
+			die("mktree reported failure");
+		if (get_sha1_hex(result.buf, sha1) < 0)
+			die("mktree did not return an object name");
+
+		strbuf_release(&result);
+	} else {
+		struct stat st;
+		int flags = HASH_FORMAT_CHECK | HASH_WRITE_OBJECT;
+
+		if (fstat(fd, &st) < 0)
+			die_errno("unable to fstat %s", filename);
+		if (index_fd(sha1, fd, &st, type, NULL, flags) < 0)
+			die("unable to write object to database");
+		/* index_fd close()s fd for us */
+	}
+
+	/*
+	 * No need to close(fd) here; both run-command and index-fd
+	 * will have done it for us.
+	 */
+}
+
+static int edit_and_replace(const char *object_ref, int force, int raw)
+{
+	char *tmpfile = git_pathdup("REPLACE_EDITOBJ");
+	enum object_type type;
+	unsigned char old[20], new[20], prev[20];
+	char ref[PATH_MAX];
+
+	if (get_sha1(object_ref, old) < 0)
+		die("Not a valid object name: '%s'", object_ref);
+
+	type = sha1_object_info(old, NULL);
+	if (type < 0)
+		die("unable to get object type for %s", sha1_to_hex(old));
+
+	check_ref_valid(old, prev, ref, sizeof(ref), force);
+
+	export_object(old, type, raw, tmpfile);
+	if (launch_editor(tmpfile, NULL, NULL) < 0)
+		die("editing object file failed");
+	import_object(new, type, raw, tmpfile);
+
+	free(tmpfile);
+
+	if (!hashcmp(old, new))
+		return error("new object is the same as the old one: '%s'", sha1_to_hex(old));
+
+	return replace_object_sha1(object_ref, old, "replacement", new, force);
+}
+
+static void replace_parents(struct strbuf *buf, int argc, const char **argv)
+{
+	struct strbuf new_parents = STRBUF_INIT;
+	const char *parent_start, *parent_end;
+	int i;
+
+	/* find existing parents */
+	parent_start = buf->buf;
+	parent_start += 46; /* "tree " + "hex sha1" + "\n" */
+	parent_end = parent_start;
+
+	while (starts_with(parent_end, "parent "))
+		parent_end += 48; /* "parent " + "hex sha1" + "\n" */
+
+	/* prepare new parents */
+	for (i = 0; i < argc; i++) {
+		unsigned char sha1[20];
+		if (get_sha1(argv[i], sha1) < 0)
+			die(_("Not a valid object name: '%s'"), argv[i]);
+		lookup_commit_or_die(sha1, argv[i]);
+		strbuf_addf(&new_parents, "parent %s\n", sha1_to_hex(sha1));
+	}
+
+	/* replace existing parents with new ones */
+	strbuf_splice(buf, parent_start - buf->buf, parent_end - parent_start,
+		      new_parents.buf, new_parents.len);
+
+	strbuf_release(&new_parents);
+}
+
+struct check_mergetag_data {
+	int argc;
+	const char **argv;
+};
+
+static void check_one_mergetag(struct commit *commit,
+			       struct commit_extra_header *extra,
+			       void *data)
+{
+	struct check_mergetag_data *mergetag_data = (struct check_mergetag_data *)data;
+	const char *ref = mergetag_data->argv[0];
+	unsigned char tag_sha1[20];
+	struct tag *tag;
+	int i;
+
+	hash_sha1_file(extra->value, extra->len, typename(OBJ_TAG), tag_sha1);
+	tag = lookup_tag(tag_sha1);
+	if (!tag)
+		die(_("bad mergetag in commit '%s'"), ref);
+	if (parse_tag_buffer(tag, extra->value, extra->len))
+		die(_("malformed mergetag in commit '%s'"), ref);
+
+	/* iterate over new parents */
+	for (i = 1; i < mergetag_data->argc; i++) {
+		unsigned char sha1[20];
+		if (get_sha1(mergetag_data->argv[i], sha1) < 0)
+			die(_("Not a valid object name: '%s'"), mergetag_data->argv[i]);
+		if (!hashcmp(tag->tagged->sha1, sha1))
+			return; /* found */
+	}
+
+	die(_("original commit '%s' contains mergetag '%s' that is discarded; "
+	      "use --edit instead of --graft"), ref, sha1_to_hex(tag_sha1));
+}
+
+static void check_mergetags(struct commit *commit, int argc, const char **argv)
+{
+	struct check_mergetag_data mergetag_data;
+
+	mergetag_data.argc = argc;
+	mergetag_data.argv = argv;
+	for_each_mergetag(check_one_mergetag, commit, &mergetag_data);
+}
+
+static int create_graft(int argc, const char **argv, int force)
+{
+	unsigned char old[20], new[20];
+	const char *old_ref = argv[0];
+	struct commit *commit;
+	struct strbuf buf = STRBUF_INIT;
+	const char *buffer;
+	unsigned long size;
+
+	if (get_sha1(old_ref, old) < 0)
+		die(_("Not a valid object name: '%s'"), old_ref);
+	commit = lookup_commit_or_die(old, old_ref);
+
+	buffer = get_commit_buffer(commit, &size);
+	strbuf_add(&buf, buffer, size);
+	unuse_commit_buffer(commit, buffer);
+
+	replace_parents(&buf, argc - 1, &argv[1]);
+
+	if (remove_signature(&buf)) {
+		warning(_("the original commit '%s' has a gpg signature."), old_ref);
+		warning(_("the signature will be removed in the replacement commit!"));
+	}
+
+	check_mergetags(commit, argc, argv);
+
+	if (write_sha1_file(buf.buf, buf.len, commit_type, new))
+		die(_("could not write replacement commit for: '%s'"), old_ref);
+
+	strbuf_release(&buf);
+
+	if (!hashcmp(old, new))
+		return error("new commit is the same as the old one: '%s'", sha1_to_hex(old));
+
+	return replace_object_sha1(old_ref, old, "replacement", new, force);
+}
+
 int cmd_replace(int argc, const char **argv, const char *prefix)
 {
-	int list = 0, delete = 0, force = 0;
+	int force = 0;
+	int raw = 0;
 	const char *format = NULL;
+	enum {
+		MODE_UNSPECIFIED = 0,
+		MODE_LIST,
+		MODE_DELETE,
+		MODE_EDIT,
+		MODE_GRAFT,
+		MODE_REPLACE
+	} cmdmode = MODE_UNSPECIFIED;
 	struct option options[] = {
-		OPT_BOOL('l', "list", &list, N_("list replace refs")),
-		OPT_BOOL('d', "delete", &delete, N_("delete replace refs")),
+		OPT_CMDMODE('l', "list", &cmdmode, N_("list replace refs"), MODE_LIST),
+		OPT_CMDMODE('d', "delete", &cmdmode, N_("delete replace refs"), MODE_DELETE),
+		OPT_CMDMODE('e', "edit", &cmdmode, N_("edit existing object"), MODE_EDIT),
+		OPT_CMDMODE('g', "graft", &cmdmode, N_("change a commit's parents"), MODE_GRAFT),
 		OPT_BOOL('f', "force", &force, N_("replace the ref if it exists")),
+		OPT_BOOL(0, "raw", &raw, N_("do not pretty-print contents for --edit")),
 		OPT_STRING(0, "format", &format, N_("format"), N_("use this format")),
 		OPT_END()
 	};
@@ -182,44 +443,56 @@ int cmd_replace(int argc, const char **argv, const char *prefix)
 
 	argc = parse_options(argc, argv, prefix, options, git_replace_usage, 0);
 
-	if (list && delete)
-		usage_msg_opt("-l and -d cannot be used together",
+	if (!cmdmode)
+		cmdmode = argc ? MODE_REPLACE : MODE_LIST;
+
+	if (format && cmdmode != MODE_LIST)
+		usage_msg_opt("--format cannot be used when not listing",
 			      git_replace_usage, options);
 
-	if (format && delete)
-		usage_msg_opt("--format and -d cannot be used together",
+	if (force &&
+	    cmdmode != MODE_REPLACE &&
+	    cmdmode != MODE_EDIT &&
+	    cmdmode != MODE_GRAFT)
+		usage_msg_opt("-f only makes sense when writing a replacement",
 			      git_replace_usage, options);
 
-	if (force && (list || delete))
-		usage_msg_opt("-f cannot be used with -d or -l",
+	if (raw && cmdmode != MODE_EDIT)
+		usage_msg_opt("--raw only makes sense with --edit",
 			      git_replace_usage, options);
 
-	/* Delete refs */
-	if (delete) {
+	switch (cmdmode) {
+	case MODE_DELETE:
 		if (argc < 1)
 			usage_msg_opt("-d needs at least one argument",
 				      git_replace_usage, options);
 		return for_each_replace_name(argv, delete_replace_ref);
-	}
 
-	/* Replace object */
-	if (!list && argc) {
+	case MODE_REPLACE:
 		if (argc != 2)
 			usage_msg_opt("bad number of arguments",
 				      git_replace_usage, options);
-		if (format)
-			usage_msg_opt("--format cannot be used when not listing",
-				      git_replace_usage, options);
 		return replace_object(argv[0], argv[1], force);
-	}
 
-	/* List refs, even if "list" is not set */
-	if (argc > 1)
-		usage_msg_opt("only one pattern can be given with -l",
-			      git_replace_usage, options);
-	if (force)
-		usage_msg_opt("-f needs some arguments",
-			      git_replace_usage, options);
+	case MODE_EDIT:
+		if (argc != 1)
+			usage_msg_opt("-e needs exactly one argument",
+				      git_replace_usage, options);
+		return edit_and_replace(argv[0], force, raw);
 
-	return list_replace_refs(argv[0], format);
+	case MODE_GRAFT:
+		if (argc < 1)
+			usage_msg_opt("-g needs at least one argument",
+				      git_replace_usage, options);
+		return create_graft(argc, argv, force);
+
+	case MODE_LIST:
+		if (argc > 1)
+			usage_msg_opt("only one pattern can be given with -l",
+				      git_replace_usage, options);
+		return list_replace_refs(argv[0], format);
+
+	default:
+		die("BUG: invalid cmdmode %d", (int)cmdmode);
+	}
 }