Merge branch 'js/deprecate-grafts'

The functionality of "$GIT_DIR/info/grafts" has been superseded by
the "refs/replace/" mechanism for some time now, but the internal
code had support for it in many places, which has been cleaned up
in order to drop support of the "grafts" mechanism.

* js/deprecate-grafts:
  Remove obsolete script to convert grafts to replace refs
  technical/shallow: describe why shallow cannot use replace refs
  technical/shallow: stop referring to grafts
  filter-branch: stop suggesting to use grafts
  Deprecate support for .git/info/grafts
  Add a test for `git replace --convert-graft-file`
  replace: introduce --convert-graft-file
  replace: prepare create_graft() for converting graft files wholesale
  replace: "libify" create_graft() and callees
  replace: avoid using die() to indicate a bug
  commit: Let the callback of for_each_mergetag return on error
  argv_array: offer to split a string by whitespace

14 files changed, 274 insertions, 118 deletions

diff --git a/Documentation/git-filter-branch.txt b/Documentation/git-filter-branch.txt
index b634043183..1d4d2f8604 100644
--- a/Documentation/git-filter-branch.txt
+++ b/Documentation/git-filter-branch.txt
@@ -288,7 +288,7 @@ git filter-branch --parent-filter \
 or even simpler:
 
 -----------------------------------------------
-echo "$commit-id $graft-id" >> .git/info/grafts
+git replace --graft $commit-id $graft-id
 git filter-branch $graft-id..HEAD
 -----------------------------------------------
 
diff --git a/Documentation/git-replace.txt b/Documentation/git-replace.txt
index e5c57ae6ef..246dc9943c 100644
--- a/Documentation/git-replace.txt
+++ b/Documentation/git-replace.txt
@@ -11,6 +11,7 @@ SYNOPSIS
 'git replace' [-f] <object> <replacement>
 'git replace' [-f] --edit <object>
 'git replace' [-f] --graft <commit> [<parent>...]
+'git replace' [-f] --convert-graft-file
 'git replace' -d <object>...
 'git replace' [--format=<format>] [-l [<pattern>]]
 
@@ -87,9 +88,13 @@ OPTIONS
 	content as <commit> except that its parents will be
 	[<parent>...] instead of <commit>'s parents. A replacement ref
 	is then created to replace <commit> with the newly created
-	commit. See contrib/convert-grafts-to-replace-refs.sh for an
-	example script based on this option that can convert grafts to
-	replace refs.
+	commit. Use `--convert-graft-file` to convert a
+	`$GIT_DIR/info/grafts` file and use replace refs instead.
+
+--convert-graft-file::
+	Creates graft commits for all entries in `$GIT_DIR/info/grafts`
+	and deletes that file upon success. The purpose is to help users
+	with transitioning off of the now-deprecated graft file.
 
 -l <pattern>::
 --list <pattern>::
diff --git a/Documentation/technical/shallow.txt b/Documentation/technical/shallow.txt
index 5183b15422..01dedfe9ff 100644
--- a/Documentation/technical/shallow.txt
+++ b/Documentation/technical/shallow.txt
@@ -8,20 +8,22 @@ repo, and therefore grafts are introduced pretending that
 these commits have no parents.
 *********************************************************
 
-The basic idea is to write the SHA-1s of shallow commits into
-$GIT_DIR/shallow, and handle its contents like the contents
-of $GIT_DIR/info/grafts (with the difference that shallow
-cannot contain parent information).
-
-This information is stored in a new file instead of grafts, or
-even the config, since the user should not touch that file
-at all (even throughout development of the shallow clone, it
-was never manually edited!).
+$GIT_DIR/shallow lists commit object names and tells Git to
+pretend as if they are root commits (e.g. "git log" traversal
+stops after showing them; "git fsck" does not complain saying
+the commits listed on their "parent" lines do not exist).
 
 Each line contains exactly one SHA-1. When read, a commit_graft
 will be constructed, which has nr_parent < 0 to make it easier
 to discern from user provided grafts.
 
+Note that the shallow feature could not be changed easily to
+use replace refs: a commit containing a `mergetag` is not allowed
+to be replaced, not even by a root commit. Such a commit can be
+made shallow, though. Also, having a `shallow` file explicitly
+listing all the commits made shallow makes it a *lot* easier to
+do shallow-specific things such as to deepen the history.
+
 Since fsck-objects relies on the library to read the objects,
 it honours shallow commits automatically.
 
diff --git a/advice.c b/advice.c
index 89fda1de55..370a56d054 100644
--- a/advice.c
+++ b/advice.c
@@ -20,6 +20,7 @@ int advice_rm_hints = 1;
 int advice_add_embedded_repo = 1;
 int advice_ignored_hook = 1;
 int advice_waiting_for_editor = 1;
+int advice_graft_file_deprecated = 1;
 
 static int advice_use_color = -1;
 static char advice_colors[][COLOR_MAXLEN] = {
@@ -70,6 +71,7 @@ static struct {
 	{ "addembeddedrepo", &advice_add_embedded_repo },
 	{ "ignoredhook", &advice_ignored_hook },
 	{ "waitingforeditor", &advice_waiting_for_editor },
+	{ "graftfiledeprecated", &advice_graft_file_deprecated },
 
 	/* make this an alias for backward compatibility */
 	{ "pushnonfastforward", &advice_push_update_rejected }
diff --git a/advice.h b/advice.h
index 70568fa792..9f5064e82a 100644
--- a/advice.h
+++ b/advice.h
@@ -21,6 +21,7 @@ extern int advice_rm_hints;
 extern int advice_add_embedded_repo;
 extern int advice_ignored_hook;
 extern int advice_waiting_for_editor;
+extern int advice_graft_file_deprecated;
 
 int git_default_advice_config(const char *var, const char *value);
 __attribute__((format (printf, 1, 2)))
diff --git a/argv-array.c b/argv-array.c
index 5d370fa336..cb5bcd2c06 100644
--- a/argv-array.c
+++ b/argv-array.c
@@ -64,6 +64,26 @@ void argv_array_pop(struct argv_array *array)
 	array->argc--;
 }
 
+void argv_array_split(struct argv_array *array, const char *to_split)
+{
+	while (isspace(*to_split))
+		to_split++;
+	for (;;) {
+		const char *p = to_split;
+
+		if (!*p)
+			break;
+
+		while (*p && !isspace(*p))
+			p++;
+		argv_array_push_nodup(array, xstrndup(to_split, p - to_split));
+
+		while (isspace(*p))
+			p++;
+		to_split = p;
+	}
+}
+
 void argv_array_clear(struct argv_array *array)
 {
 	if (array->argv != empty_argv) {
diff --git a/argv-array.h b/argv-array.h
index 29056e49a1..750c30d2f2 100644
--- a/argv-array.h
+++ b/argv-array.h
@@ -19,6 +19,8 @@ LAST_ARG_MUST_BE_NULL
 void argv_array_pushl(struct argv_array *, ...);
 void argv_array_pushv(struct argv_array *, const char **);
 void argv_array_pop(struct argv_array *);
+/* Splits by whitespace; does not handle quoted arguments! */
+void argv_array_split(struct argv_array *, const char *);
 void argv_array_clear(struct argv_array *);
 const char **argv_array_detach(struct argv_array *);
 
diff --git a/builtin/replace.c b/builtin/replace.c
index 14e142d5a8..6da2411e14 100644
--- a/builtin/replace.c
+++ b/builtin/replace.c
@@ -22,6 +22,7 @@ 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 [-f] --convert-graft-file"),
 	N_("git replace -d <object>..."),
 	N_("git replace [--format=<format>] [-l [<pattern>]]"),
 	NULL
@@ -82,9 +83,9 @@ static int list_replace_refs(const char *pattern, const char *format)
 	else if (!strcmp(format, "long"))
 		data.format = REPLACE_FORMAT_LONG;
 	else
-		die("invalid replace format '%s'\n"
-		    "valid formats are 'short', 'medium' and 'long'\n",
-		    format);
+		return error("invalid replace format '%s'\n"
+			     "valid formats are 'short', 'medium' and 'long'\n",
+			     format);
 
 	for_each_replace_ref(the_repository, show_reference, (void *)&data);
 
@@ -137,7 +138,7 @@ static int delete_replace_ref(const char *name, const char *ref,
 	return 0;
 }
 
-static void check_ref_valid(struct object_id *object,
+static int check_ref_valid(struct object_id *object,
 			    struct object_id *prev,
 			    struct strbuf *ref,
 			    int force)
@@ -145,12 +146,13 @@ static void check_ref_valid(struct object_id *object,
 	strbuf_reset(ref);
 	strbuf_addf(ref, "%s%s", git_replace_ref_base, oid_to_hex(object));
 	if (check_refname_format(ref->buf, 0))
-		die("'%s' is not a valid ref name.", ref->buf);
+		return error("'%s' is not a valid ref name.", ref->buf);
 
 	if (read_ref(ref->buf, prev))
 		oidclr(prev);
 	else if (!force)
-		die("replace ref '%s' already exists", ref->buf);
+		return error("replace ref '%s' already exists", ref->buf);
+	return 0;
 }
 
 static int replace_object_oid(const char *object_ref,
@@ -164,28 +166,33 @@ static int replace_object_oid(const char *object_ref,
 	struct strbuf ref = STRBUF_INIT;
 	struct ref_transaction *transaction;
 	struct strbuf err = STRBUF_INIT;
+	int res = 0;
 
 	obj_type = oid_object_info(the_repository, object, NULL);
 	repl_type = oid_object_info(the_repository, repl, NULL);
 	if (!force && obj_type != repl_type)
-		die("Objects must be of the same type.\n"
-		    "'%s' points to a replaced object of type '%s'\n"
-		    "while '%s' points to a replacement object of type '%s'.",
-		    object_ref, type_name(obj_type),
-		    replace_ref, type_name(repl_type));
-
-	check_ref_valid(object, &prev, &ref, force);
+		return error("Objects must be of the same type.\n"
+			     "'%s' points to a replaced object of type '%s'\n"
+			     "while '%s' points to a replacement object of "
+			     "type '%s'.",
+			     object_ref, type_name(obj_type),
+			     replace_ref, type_name(repl_type));
+
+	if (check_ref_valid(object, &prev, &ref, force)) {
+		strbuf_release(&ref);
+		return -1;
+	}
 
 	transaction = ref_transaction_begin(&err);
 	if (!transaction ||
 	    ref_transaction_update(transaction, ref.buf, repl, &prev,
 				   0, NULL, &err) ||
 	    ref_transaction_commit(transaction, &err))
-		die("%s", err.buf);
+		res = error("%s", err.buf);
 
 	ref_transaction_free(transaction);
 	strbuf_release(&ref);
-	return 0;
+	return res;
 }
 
 static int replace_object(const char *object_ref, const char *replace_ref, int force)
@@ -193,9 +200,11 @@ static int replace_object(const char *object_ref, const char *replace_ref, int f
 	struct object_id object, repl;
 
 	if (get_oid(object_ref, &object))
-		die("Failed to resolve '%s' as a valid ref.", object_ref);
+		return error("Failed to resolve '%s' as a valid ref.",
+			     object_ref);
 	if (get_oid(replace_ref, &repl))
-		die("Failed to resolve '%s' as a valid ref.", replace_ref);
+		return error("Failed to resolve '%s' as a valid ref.",
+			     replace_ref);
 
 	return replace_object_oid(object_ref, &object, replace_ref, &repl, force);
 }
@@ -205,7 +214,7 @@ static int replace_object(const char *object_ref, const char *replace_ref, int f
  * 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 struct object_id *oid, enum object_type type,
+static int export_object(const struct object_id *oid, enum object_type type,
 			  int raw, const char *filename)
 {
 	struct child_process cmd = CHILD_PROCESS_INIT;
@@ -213,7 +222,7 @@ static void export_object(const struct object_id *oid, enum object_type type,
 
 	fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
 	if (fd < 0)
-		die_errno("unable to open %s for writing", filename);
+		return error_errno("unable to open %s for writing", filename);
 
 	argv_array_push(&cmd.args, "--no-replace-objects");
 	argv_array_push(&cmd.args, "cat-file");
@@ -226,7 +235,8 @@ static void export_object(const struct object_id *oid, enum object_type type,
 	cmd.out = fd;
 
 	if (run_command(&cmd))
-		die("cat-file reported failure");
+		return error("cat-file reported failure");
+	return 0;
 }
 
 /*
@@ -234,14 +244,14 @@ static void export_object(const struct object_id *oid, enum object_type type,
  * 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(struct object_id *oid, enum object_type type,
+static int import_object(struct object_id *oid, 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);
+		return error_errno("unable to open %s for reading", filename);
 
 	if (!raw && type == OBJ_TREE) {
 		const char *argv[] = { "mktree", NULL };
@@ -253,27 +263,40 @@ static void import_object(struct object_id *oid, enum object_type type,
 		cmd.in = fd;
 		cmd.out = -1;
 
-		if (start_command(&cmd))
-			die("unable to spawn mktree");
+		if (start_command(&cmd)) {
+			close(fd);
+			return error("unable to spawn mktree");
+		}
 
-		if (strbuf_read(&result, cmd.out, 41) < 0)
-			die_errno("unable to read from mktree");
+		if (strbuf_read(&result, cmd.out, 41) < 0) {
+			error_errno("unable to read from mktree");
+			close(fd);
+			close(cmd.out);
+			return -1;
+		}
 		close(cmd.out);
 
-		if (finish_command(&cmd))
-			die("mktree reported failure");
-		if (get_oid_hex(result.buf, oid) < 0)
-			die("mktree did not return an object name");
+		if (finish_command(&cmd)) {
+			strbuf_release(&result);
+			return error("mktree reported failure");
+		}
+		if (get_oid_hex(result.buf, oid) < 0) {
+			strbuf_release(&result);
+			return error("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 (fstat(fd, &st) < 0) {
+			error_errno("unable to fstat %s", filename);
+			close(fd);
+			return -1;
+		}
 		if (index_fd(oid, fd, &st, type, NULL, flags) < 0)
-			die("unable to write object to database");
+			return error("unable to write object to database");
 		/* index_fd close()s fd for us */
 	}
 
@@ -281,30 +304,43 @@ static void import_object(struct object_id *oid, enum object_type type,
 	 * No need to close(fd) here; both run-command and index-fd
 	 * will have done it for us.
 	 */
+	return 0;
 }
 
 static int edit_and_replace(const char *object_ref, int force, int raw)
 {
-	char *tmpfile = git_pathdup("REPLACE_EDITOBJ");
+	char *tmpfile;
 	enum object_type type;
 	struct object_id old_oid, new_oid, prev;
 	struct strbuf ref = STRBUF_INIT;
 
 	if (get_oid(object_ref, &old_oid) < 0)
-		die("Not a valid object name: '%s'", object_ref);
+		return error("Not a valid object name: '%s'", object_ref);
 
 	type = oid_object_info(the_repository, &old_oid, NULL);
 	if (type < 0)
-		die("unable to get object type for %s", oid_to_hex(&old_oid));
+		return error("unable to get object type for %s",
+			     oid_to_hex(&old_oid));
 
-	check_ref_valid(&old_oid, &prev, &ref, force);
+	if (check_ref_valid(&old_oid, &prev, &ref, force)) {
+		strbuf_release(&ref);
+		return -1;
+	}
 	strbuf_release(&ref);
 
-	export_object(&old_oid, type, raw, tmpfile);
-	if (launch_editor(tmpfile, NULL, NULL) < 0)
-		die("editing object file failed");
-	import_object(&new_oid, type, raw, tmpfile);
-
+	tmpfile = git_pathdup("REPLACE_EDITOBJ");
+	if (export_object(&old_oid, type, raw, tmpfile)) {
+		free(tmpfile);
+		return -1;
+	}
+	if (launch_editor(tmpfile, NULL, NULL) < 0) {
+		free(tmpfile);
+		return error("editing object file failed");
+	}
+	if (import_object(&new_oid, type, raw, tmpfile)) {
+		free(tmpfile);
+		return -1;
+	}
 	free(tmpfile);
 
 	if (!oidcmp(&old_oid, &new_oid))
@@ -313,7 +349,7 @@ static int edit_and_replace(const char *object_ref, int force, int raw)
 	return replace_object_oid(object_ref, &old_oid, "replacement", &new_oid, force);
 }
 
-static void replace_parents(struct strbuf *buf, int argc, const char **argv)
+static int replace_parents(struct strbuf *buf, int argc, const char **argv)
 {
 	struct strbuf new_parents = STRBUF_INIT;
 	const char *parent_start, *parent_end;
@@ -330,9 +366,15 @@ static void replace_parents(struct strbuf *buf, int argc, const char **argv)
 	/* prepare new parents */
 	for (i = 0; i < argc; i++) {
 		struct object_id oid;
-		if (get_oid(argv[i], &oid) < 0)
-			die(_("Not a valid object name: '%s'"), argv[i]);
-		lookup_commit_or_die(&oid, argv[i]);
+		if (get_oid(argv[i], &oid) < 0) {
+			strbuf_release(&new_parents);
+			return error(_("Not a valid object name: '%s'"),
+				     argv[i]);
+		}
+		if (!lookup_commit_reference(&oid)) {
+			strbuf_release(&new_parents);
+			return error(_("could not parse %s"), argv[i]);
+		}
 		strbuf_addf(&new_parents, "parent %s\n", oid_to_hex(&oid));
 	}
 
@@ -341,6 +383,7 @@ static void replace_parents(struct strbuf *buf, int argc, const char **argv)
 		      new_parents.buf, new_parents.len);
 
 	strbuf_release(&new_parents);
+	return 0;
 }
 
 struct check_mergetag_data {
@@ -348,7 +391,7 @@ struct check_mergetag_data {
 	const char **argv;
 };
 
-static void check_one_mergetag(struct commit *commit,
+static int check_one_mergetag(struct commit *commit,
 			       struct commit_extra_header *extra,
 			       void *data)
 {
@@ -361,33 +404,35 @@ static void check_one_mergetag(struct commit *commit,
 	hash_object_file(extra->value, extra->len, type_name(OBJ_TAG), &tag_oid);
 	tag = lookup_tag(&tag_oid);
 	if (!tag)
-		die(_("bad mergetag in commit '%s'"), ref);
+		return error(_("bad mergetag in commit '%s'"), ref);
 	if (parse_tag_buffer(tag, extra->value, extra->len))
-		die(_("malformed mergetag in commit '%s'"), ref);
+		return error(_("malformed mergetag in commit '%s'"), ref);
 
 	/* iterate over new parents */
 	for (i = 1; i < mergetag_data->argc; i++) {
 		struct object_id oid;
 		if (get_oid(mergetag_data->argv[i], &oid) < 0)
-			die(_("Not a valid object name: '%s'"), mergetag_data->argv[i]);
+			return error(_("Not a valid object name: '%s'"),
+				     mergetag_data->argv[i]);
 		if (!oidcmp(&tag->tagged->oid, &oid))
-			return; /* found */
+			return 0; /* found */
 	}
 
-	die(_("original commit '%s' contains mergetag '%s' that is discarded; "
-	      "use --edit instead of --graft"), ref, oid_to_hex(&tag_oid));
+	return error(_("original commit '%s' contains mergetag '%s' that is "
+		       "discarded; use --edit instead of --graft"), ref,
+		     oid_to_hex(&tag_oid));
 }
 
-static void check_mergetags(struct commit *commit, int argc, const char **argv)
+static int 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);
+	return for_each_mergetag(check_one_mergetag, commit, &mergetag_data);
 }
 
-static int create_graft(int argc, const char **argv, int force)
+static int create_graft(int argc, const char **argv, int force, int gentle)
 {
 	struct object_id old_oid, new_oid;
 	const char *old_ref = argv[0];
@@ -397,33 +442,81 @@ static int create_graft(int argc, const char **argv, int force)
 	unsigned long size;
 
 	if (get_oid(old_ref, &old_oid) < 0)
-		die(_("Not a valid object name: '%s'"), old_ref);
-	commit = lookup_commit_or_die(&old_oid, old_ref);
+		return error(_("Not a valid object name: '%s'"), old_ref);
+	commit = lookup_commit_reference(&old_oid);
+	if (!commit)
+		return error(_("could not parse %s"), 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 (replace_parents(&buf, argc - 1, &argv[1]) < 0) {
+		strbuf_release(&buf);
+		return -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 (check_mergetags(commit, argc, argv)) {
+		strbuf_release(&buf);
+		return -1;
+	}
 
-	if (write_object_file(buf.buf, buf.len, commit_type, &new_oid))
-		die(_("could not write replacement commit for: '%s'"), old_ref);
+	if (write_object_file(buf.buf, buf.len, commit_type, &new_oid)) {
+		strbuf_release(&buf);
+		return error(_("could not write replacement commit for: '%s'"),
+			     old_ref);
+	}
 
 	strbuf_release(&buf);
 
-	if (!oidcmp(&old_oid, &new_oid))
+	if (!oidcmp(&old_oid, &new_oid)) {
+		if (gentle) {
+			warning("graft for '%s' unnecessary", oid_to_hex(&old_oid));
+			return 0;
+		}
 		return error("new commit is the same as the old one: '%s'", oid_to_hex(&old_oid));
+	}
 
 	return replace_object_oid(old_ref, &old_oid, "replacement", &new_oid, force);
 }
 
+static int convert_graft_file(int force)
+{
+	const char *graft_file = get_graft_file();
+	FILE *fp = fopen_or_warn(graft_file, "r");
+	struct strbuf buf = STRBUF_INIT, err = STRBUF_INIT;
+	struct argv_array args = ARGV_ARRAY_INIT;
+
+	if (!fp)
+		return -1;
+
+	while (strbuf_getline(&buf, fp) != EOF) {
+		if (*buf.buf == '#')
+			continue;
+
+		argv_array_split(&args, buf.buf);
+		if (args.argc && create_graft(args.argc, args.argv, force, 1))
+			strbuf_addf(&err, "\n\t%s", buf.buf);
+		argv_array_clear(&args);
+	}
+	fclose(fp);
+
+	strbuf_release(&buf);
+
+	if (!err.len)
+		return unlink_or_warn(graft_file);
+
+	warning(_("could not convert the following graft(s):\n%s"), err.buf);
+	strbuf_release(&err);
+
+	return -1;
+}
+
 int cmd_replace(int argc, const char **argv, const char *prefix)
 {
 	int force = 0;
@@ -435,6 +528,7 @@ int cmd_replace(int argc, const char **argv, const char *prefix)
 		MODE_DELETE,
 		MODE_EDIT,
 		MODE_GRAFT,
+		MODE_CONVERT_GRAFT_FILE,
 		MODE_REPLACE
 	} cmdmode = MODE_UNSPECIFIED;
 	struct option options[] = {
@@ -442,6 +536,7 @@ int cmd_replace(int argc, const char **argv, const char *prefix)
 		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_CMDMODE(0, "convert-graft-file", &cmdmode, N_("convert existing graft file"), MODE_CONVERT_GRAFT_FILE),
 		OPT_BOOL_F('f', "force", &force, N_("replace the ref if it exists"),
 			   PARSE_OPT_NOCOMPLETE),
 		OPT_BOOL(0, "raw", &raw, N_("do not pretty-print contents for --edit")),
@@ -464,7 +559,8 @@ int cmd_replace(int argc, const char **argv, const char *prefix)
 	if (force &&
 	    cmdmode != MODE_REPLACE &&
 	    cmdmode != MODE_EDIT &&
-	    cmdmode != MODE_GRAFT)
+	    cmdmode != MODE_GRAFT &&
+	    cmdmode != MODE_CONVERT_GRAFT_FILE)
 		usage_msg_opt("-f only makes sense when writing a replacement",
 			      git_replace_usage, options);
 
@@ -495,7 +591,13 @@ int cmd_replace(int argc, const char **argv, const char *prefix)
 		if (argc < 1)
 			usage_msg_opt("-g needs at least one argument",
 				      git_replace_usage, options);
-		return create_graft(argc, argv, force);
+		return create_graft(argc, argv, force, 0);
+
+	case MODE_CONVERT_GRAFT_FILE:
+		if (argc != 0)
+			usage_msg_opt("--convert-graft-file takes no argument",
+				      git_replace_usage, options);
+		return !!convert_graft_file(force);
 
 	case MODE_LIST:
 		if (argc > 1)
@@ -504,6 +606,6 @@ int cmd_replace(int argc, const char **argv, const char *prefix)
 		return list_replace_refs(argv[0], format);
 
 	default:
-		die("BUG: invalid cmdmode %d", (int)cmdmode);
+		BUG("invalid cmdmode %d", (int)cmdmode);
 	}
 }
diff --git a/commit.c b/commit.c
index 1d7622b2cc..f9714ed74c 100644
--- a/commit.c
+++ b/commit.c
@@ -13,6 +13,7 @@
 #include "prio-queue.h"
 #include "sha1-lookup.h"
 #include "wt-status.h"
+#include "advice.h"
 
 static struct commit_extra_header *read_commit_extra_header_lines(const char *buf, size_t len, const char **);
 
@@ -177,6 +178,15 @@ static int read_graft_file(const char *graft_file)
 	struct strbuf buf = STRBUF_INIT;
 	if (!fp)
 		return -1;
+	if (advice_graft_file_deprecated)
+		advise(_("Support for <GIT_DIR>/info/grafts is deprecated\n"
+			 "and will be removed in a future Git version.\n"
+			 "\n"
+			 "Please use \"git replace --convert-graft-file\"\n"
+			 "to convert the grafts into replace refs.\n"
+			 "\n"
+			 "Turn this message off by running\n"
+			 "\"git config advice.graftFileDeprecated false\""));
 	while (!strbuf_getwholeline(&buf, fp, '\n')) {
 		/* The format is just "Commit Parent1 Parent2 ...\n" */
 		struct commit_graft *graft = read_graft_line(&buf);
@@ -1307,17 +1317,19 @@ struct commit_extra_header *read_commit_extra_headers(struct commit *commit,
 	return extra;
 }
 
-void for_each_mergetag(each_mergetag_fn fn, struct commit *commit, void *data)
+int for_each_mergetag(each_mergetag_fn fn, struct commit *commit, void *data)
 {
 	struct commit_extra_header *extra, *to_free;
+	int res = 0;
 
 	to_free = read_commit_extra_headers(commit, NULL);
-	for (extra = to_free; extra; extra = extra->next) {
+	for (extra = to_free; !res && extra; extra = extra->next) {
 		if (strcmp(extra->key, "mergetag"))
 			continue; /* not a merge tag */
-		fn(commit, extra, data);
+		res = fn(commit, extra, data);
 	}
 	free_commit_extra_headers(to_free);
+	return res;
 }
 
 static inline int standard_header_field(const char *field, size_t len)
diff --git a/commit.h b/commit.h
index 23a3f364ed..10e34e1a18 100644
--- a/commit.h
+++ b/commit.h
@@ -303,10 +303,10 @@ extern const char *find_commit_header(const char *msg, const char *key,
 /* Find the end of the log message, the right place for a new trailer. */
 extern int ignore_non_trailer(const char *buf, size_t len);
 
-typedef void (*each_mergetag_fn)(struct commit *commit, struct commit_extra_header *extra,
+typedef int (*each_mergetag_fn)(struct commit *commit, struct commit_extra_header *extra,
 				 void *cb_data);
 
-extern void for_each_mergetag(each_mergetag_fn fn, struct commit *commit, void *data);
+extern int for_each_mergetag(each_mergetag_fn fn, struct commit *commit, void *data);
 
 struct merge_remote_desc {
 	struct object *obj; /* the named object, could be a tag */
diff --git a/contrib/convert-grafts-to-replace-refs.sh b/contrib/convert-grafts-to-replace-refs.sh
deleted file mode 100755
index 0cbc917b8c..0000000000
--- a/contrib/convert-grafts-to-replace-refs.sh
+++ /dev/null
@@ -1,28 +0,0 @@
-#!/bin/sh
-
-# You should execute this script in the repository where you
-# want to convert grafts to replace refs.
-
-GRAFTS_FILE="${GIT_DIR:-.git}/info/grafts"
-
-. $(git --exec-path)/git-sh-setup
-
-test -f "$GRAFTS_FILE" || die "Could not find graft file: '$GRAFTS_FILE'"
-
-grep '^[^# ]' "$GRAFTS_FILE" |
-while read definition
-do
-	if test -n "$definition"
-	then
-		echo "Converting: $definition"
-		git replace --graft $definition ||
-			die "Conversion failed for: $definition"
-	fi
-done
-
-mv "$GRAFTS_FILE" "$GRAFTS_FILE.bak" ||
-	die "Could not rename '$GRAFTS_FILE' to '$GRAFTS_FILE.bak'"
-
-echo "Success!"
-echo "All the grafts in '$GRAFTS_FILE' have been converted to replace refs!"
-echo "The grafts file '$GRAFTS_FILE' has been renamed: '$GRAFTS_FILE.bak'"
diff --git a/log-tree.c b/log-tree.c
index 2e6b486140..66329d089d 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -488,9 +488,9 @@ static int is_common_merge(const struct commit *commit)
 		&& !commit->parents->next->next);
 }
 
-static void show_one_mergetag(struct commit *commit,
-			      struct commit_extra_header *extra,
-			      void *data)
+static int show_one_mergetag(struct commit *commit,
+			     struct commit_extra_header *extra,
+			     void *data)
 {
 	struct rev_info *opt = (struct rev_info *)data;
 	struct object_id oid;
@@ -502,7 +502,7 @@ static void show_one_mergetag(struct commit *commit,
 	hash_object_file(extra->value, extra->len, type_name(OBJ_TAG), &oid);
 	tag = lookup_tag(&oid);
 	if (!tag)
-		return; /* error message already given */
+		return -1; /* error message already given */
 
 	strbuf_init(&verify_message, 256);
 	if (parse_tag_buffer(tag, extra->value, extra->len))
@@ -536,11 +536,12 @@ static void show_one_mergetag(struct commit *commit,
 
 	show_sig_lines(opt, status, verify_message.buf);
 	strbuf_release(&verify_message);
+	return 0;
 }
 
-static void show_mergetag(struct rev_info *opt, struct commit *commit)
+static int show_mergetag(struct rev_info *opt, struct commit *commit)
 {
-	for_each_mergetag(show_one_mergetag, commit, opt);
+	return for_each_mergetag(show_one_mergetag, commit, opt);
 }
 
 void show_log(struct rev_info *opt)
diff --git a/t/t6001-rev-list-graft.sh b/t/t6001-rev-list-graft.sh
index 05ddc69cf2..7504ba4751 100755
--- a/t/t6001-rev-list-graft.sh
+++ b/t/t6001-rev-list-graft.sh
@@ -110,4 +110,13 @@ do
 	"
 
 done
+
+test_expect_success 'show advice that grafts are deprecated' '
+	git show HEAD 2>err &&
+	test_i18ngrep "git replace" err &&
+	test_config advice.graftFileDeprecated false &&
+	git show HEAD 2>err &&
+	test_i18ngrep ! "git replace" err
+'
+
 test_done
diff --git a/t/t6050-replace.sh b/t/t6050-replace.sh
index c630aba657..d174bfed30 100755
--- a/t/t6050-replace.sh
+++ b/t/t6050-replace.sh
@@ -444,4 +444,32 @@ test_expect_success GPG '--graft on a commit with a mergetag' '
 	git replace -d $HASH10
 '
 
+test_expect_success '--convert-graft-file' '
+	git checkout -b with-graft-file &&
+	test_commit root2 &&
+	git reset --hard root2^ &&
+	test_commit root1 &&
+	test_commit after-root1 &&
+	test_tick &&
+	git merge -m merge-root2 root2 &&
+
+	: add and convert graft file &&
+	printf "%s\n%s %s\n\n# comment\n%s\n" \
+		$(git rev-parse HEAD^^ HEAD^ HEAD^^ HEAD^2) \
+		>.git/info/grafts &&
+	git replace --convert-graft-file &&
+	test_path_is_missing .git/info/grafts &&
+
+	: verify that the history is now "grafted" &&
+	git rev-list HEAD >out &&
+	test_line_count = 4 out &&
+
+	: create invalid graft file and verify that it is not deleted &&
+	test_when_finished "rm -f .git/info/grafts" &&
+	echo $EMPTY_BLOB $EMPTY_TREE >.git/info/grafts &&
+	test_must_fail git replace --convert-graft-file 2>err &&
+	test_i18ngrep "$EMPTY_BLOB $EMPTY_TREE" err &&
+	test_i18ngrep "$EMPTY_BLOB $EMPTY_TREE" .git/info/grafts
+'
+
 test_done