diff --git a/Documentation/config/branch.adoc b/Documentation/config/branch.adoc
index a4db9fa5c8..6c1b5bb9cd 100644
--- a/Documentation/config/branch.adoc
+++ b/Documentation/config/branch.adoc
@@ -102,3 +102,10 @@ for details).
 	`git branch --edit-description`. Branch description is
 	automatically added to the `format-patch` cover letter or
 	`request-pull` summary.
+
+`branch.<name>.pruneMerged`::
+	If set to `false`, branch _<name>_ is exempt from
+	`git branch --prune-merged`.  Useful for a topic branch you
+	intend to develop further after an initial round has been
+	merged upstream.  Defaults to true.  Explicit deletion via
+	`git branch -d` is unaffected.
diff --git a/Documentation/git-branch.adoc b/Documentation/git-branch.adoc
index c0afddc424..c579df4fe0 100644
--- a/Documentation/git-branch.adoc
+++ b/Documentation/git-branch.adoc
@@ -14,6 +14,7 @@ git branch [--color[=<when>] | --no-color] [--show-current]
 	   [--merged [<commit>]] [--no-merged [<commit>]]
 	   [--contains [<commit>]] [--no-contains [<commit>]]
 	   [--points-at <object>] [--format=<format>]
+	   [(--forked <branch>)...]
 	   [(-r|--remotes) | (-a|--all)]
 	   [--list] [<pattern>...]
 git branch [--track[=(direct|inherit)] | --no-track] [-f]
@@ -24,6 +25,7 @@ git branch (-m|-M) [<old-branch>] <new-branch>
 git branch (-c|-C) [<old-branch>] <new-branch>
 git branch (-d|-D) [-r] <branch-name>...
 git branch --edit-description [<branch-name>]
+git branch [--dry-run] (--prune-merged <branch>)...
 
 DESCRIPTION
 -----------
@@ -199,6 +201,41 @@ This option is only applicable in non-verbose mode.
 	Print the name of the current branch. In detached `HEAD` state,
 	nothing is printed.
 
+`--forked <branch>`::
+	List only branches whose configured upstream matches
+	_<branch>_. The argument can be a ref (e.g. `origin/main`,
+	`master`) or a shell-style glob (e.g. `'origin/*'`). The
+	option can be repeated to widen the filter.
+
+`--prune-merged <branch>`::
+	Delete the local branches that `--forked` would list for the
+	same _<branch>_, but only those whose tip is reachable from
+	their configured upstream. In other words, the work on the
+	branch has already landed on the upstream it tracks, so the
+	local copy is no longer needed. May be given more than once to
+	union the matches; positional arguments are not accepted.
++
+Reachability is checked against whatever the upstream refs say
+locally; nothing is fetched. Run `git fetch` first if you want
+the upstream refs refreshed.
++
+A branch is left alone if any of the following holds:
+its upstream no longer resolves locally; it is checked out in any
+worktree; its push destination (`<branch>@{push}`) equals its
+upstream (`<branch>@{upstream}`), so it cannot be distinguished
+from a freshly pulled trunk that just looks "fully merged"; or
+`branch.<name>.pruneMerged` is set to `false`.
++
+Branches refused by the "fully merged" safety check are listed as
+warnings and skipped; pass them to `git branch -D` explicitly if
+you want them gone.
+
+`--dry-run`::
+	With `--prune-merged`, print which branches would be
+	deleted and exit without touching any ref.  Useful for
+	sanity-checking a wide pattern like `'origin/*'` before
+	committing to the deletion.
+
 `-v`::
 `-vv`::
 `--verbose`::
diff --git a/builtin/branch.c b/builtin/branch.c
index 1572a4f9ef..1811511b9e 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -28,9 +28,10 @@
 #include "help.h"
 #include "advice.h"
 #include "commit-reach.h"
+#include "wildmatch.h"
 
 static const char * const builtin_branch_usage[] = {
-	N_("git branch [<options>] [-r | -a] [--merged] [--no-merged]"),
+	N_("git branch [<options>] [-r | -a] [--merged] [--no-merged] [(--forked <branch>)...]"),
 	N_("git branch [<options>] [-f] [--recurse-submodules] <branch-name> [<start-point>]"),
 	N_("git branch [<options>] [-l] [<pattern>...]"),
 	N_("git branch [<options>] [-r] (-d | -D) <branch-name>..."),
@@ -38,6 +39,7 @@ static const char * const builtin_branch_usage[] = {
 	N_("git branch [<options>] (-c | -C) [<old-branch>] <new-branch>"),
 	N_("git branch [<options>] [-r | -a] [--points-at]"),
 	N_("git branch [<options>] [-r | -a] [--format]"),
+	N_("git branch [<options>] (--prune-merged <branch>)..."),
 	NULL
 };
 
@@ -168,10 +170,13 @@ static int branch_merged(int kind, const char *name,
 	 * upstream, if any, otherwise with HEAD", we should just
 	 * return the result of the repo_in_merge_bases() above without
 	 * any of the following code, but during the transition period,
-	 * a gentle reminder is in order.
+	 * a gentle reminder is in order.  Callers that opt out of the
+	 * HEAD fallback by passing head_rev=NULL are not interested in
+	 * the reminder either: they have already established that the
+	 * branch has an upstream, so HEAD is irrelevant to the decision.
 	 */
-	if (head_rev != reference_rev) {
-		int expect = head_rev ? repo_in_merge_bases(the_repository, rev, head_rev) : 0;
+	if (head_rev && head_rev != reference_rev) {
+		int expect = repo_in_merge_bases(the_repository, rev, head_rev);
 		if (expect < 0)
 			exit(128);
 		if (expect == merged)
@@ -191,7 +196,7 @@ static int branch_merged(int kind, const char *name,
 
 static int check_branch_commit(const char *branchname, const char *refname,
 			       const struct object_id *oid, struct commit *head_rev,
-			       int kinds, int force)
+			       int kinds, int force, int warn_only)
 {
 	struct commit *rev = lookup_commit_reference(the_repository, oid);
 	if (!force && !rev) {
@@ -199,10 +204,16 @@ static int check_branch_commit(const char *branchname, const char *refname,
 		return -1;
 	}
 	if (!force && !branch_merged(kinds, branchname, rev, head_rev)) {
-		error(_("the branch '%s' is not fully merged"), branchname);
-		advise_if_enabled(ADVICE_FORCE_DELETE_BRANCH,
-				  _("If you are sure you want to delete it, "
-				  "run 'git branch -D %s'"), branchname);
+		if (warn_only) {
+			warning(_("the branch '%s' is not fully merged"),
+				branchname);
+		} else {
+			error(_("the branch '%s' is not fully merged"),
+			      branchname);
+			advise_if_enabled(ADVICE_FORCE_DELETE_BRANCH,
+					  _("If you are sure you want to delete it, "
+					  "run 'git branch -D %s'"), branchname);
+		}
 		return -1;
 	}
 	return 0;
@@ -218,7 +229,8 @@ static void delete_branch_config(const char *branchname)
 }
 
 static int delete_branches(int argc, const char **argv, int force, int kinds,
-			   int quiet)
+			   int quiet, int warn_only, int no_head_fallback,
+			   int dry_run)
 {
 	struct commit *head_rev = NULL;
 	struct object_id oid;
@@ -252,7 +264,7 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 	}
 	branch_name_pos = strcspn(fmt, "%");
 
-	if (!force)
+	if (!force && !no_head_fallback)
 		head_rev = lookup_commit_reference(the_repository, &head_oid);
 
 	for (i = 0; i < argc; i++, strbuf_reset(&bname)) {
@@ -308,8 +320,9 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 
 		if (!(flags & (REF_ISSYMREF|REF_ISBROKEN)) &&
 		    check_branch_commit(bname.buf, name, &oid, head_rev, kinds,
-					force)) {
-			ret = 1;
+					force, warn_only)) {
+			if (!warn_only)
+				ret = 1;
 			goto next;
 		}
 
@@ -322,13 +335,20 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 		free(target);
 	}
 
-	if (refs_delete_refs(get_main_ref_store(the_repository), NULL, &refs_to_delete, REF_NO_DEREF))
+	if (!dry_run &&
+	    refs_delete_refs(get_main_ref_store(the_repository), NULL, &refs_to_delete, REF_NO_DEREF))
 		ret = 1;
 
 	for_each_string_list_item(item, &refs_to_delete) {
 		char *describe_ref = item->util;
 		char *name = item->string;
-		if (!refs_ref_exists(get_main_ref_store(the_repository), name)) {
+		if (dry_run) {
+			if (!quiet)
+				printf(remote_branch
+					? _("Would delete remote-tracking branch %s (was %s).\n")
+					: _("Would delete branch %s (was %s).\n"),
+					name + branch_name_pos, describe_ref);
+		} else if (!refs_ref_exists(get_main_ref_store(the_repository), name)) {
 			char *refname = name + branch_name_pos;
 			if (!quiet)
 				printf(remote_branch
@@ -442,8 +462,12 @@ static char *build_format(struct ref_filter *filter, int maxwidth, const char *r
 	return strbuf_detach(&fmt, NULL);
 }
 
+static void filter_array_by_forked(struct ref_array *array,
+				   const struct string_list *upstreams);
+
 static void print_ref_list(struct ref_filter *filter, struct ref_sorting *sorting,
-			   struct ref_format *format, struct string_list *output)
+			   struct ref_format *format, struct string_list *output,
+			   const struct string_list *forked_upstreams)
 {
 	int i;
 	struct ref_array array;
@@ -463,6 +487,9 @@ static void print_ref_list(struct ref_filter *filter, struct ref_sorting *sortin
 
 	filter_refs(&array, filter, filter->kind);
 
+	if (forked_upstreams->nr)
+		filter_array_by_forked(&array, forked_upstreams);
+
 	if (filter->verbose)
 		maxwidth = calc_maxwidth(&array, strlen(remote_prefix));
 
@@ -673,6 +700,230 @@ static void copy_or_rename_branch(const char *oldname, const char *newname, int
 	free_worktrees(worktrees);
 }
 
+struct upstream_pattern {
+	char *name;
+	int is_wildcard;
+};
+
+static void upstream_pattern_list_clear(struct upstream_pattern *items,
+					size_t nr)
+{
+	size_t i;
+	for (i = 0; i < nr; i++)
+		free(items[i].name);
+	free(items);
+}
+
+static const char *short_upstream_name(const char *full_ref)
+{
+	const char *short_name = full_ref;
+	(void)(skip_prefix(short_name, "refs/heads/", &short_name) ||
+	       skip_prefix(short_name, "refs/remotes/", &short_name));
+	return short_name;
+}
+
+static int parse_one_forked_arg(const char *arg, struct upstream_pattern *out)
+{
+	struct object_id oid;
+	char *full_ref = NULL;
+
+	if (has_glob_specials(arg)) {
+		out->name = xstrdup(arg);
+		out->is_wildcard = 1;
+		return 0;
+	}
+
+	if (repo_dwim_ref(the_repository, arg, strlen(arg), &oid,
+			  &full_ref, 0) == 1 &&
+	    (starts_with(full_ref, "refs/heads/") ||
+	     starts_with(full_ref, "refs/remotes/"))) {
+		out->name = xstrdup(short_upstream_name(full_ref));
+		out->is_wildcard = 0;
+		free(full_ref);
+		return 0;
+	}
+	free(full_ref);
+	return -1;
+}
+
+static void parse_forked_args(const struct string_list *args,
+			      struct upstream_pattern **patterns_out,
+			      size_t *nr_out)
+{
+	struct upstream_pattern *patterns;
+	size_t i;
+
+	ALLOC_ARRAY(patterns, args->nr);
+	for (i = 0; i < args->nr; i++) {
+		const char *arg = args->items[i].string;
+		if (parse_one_forked_arg(arg, &patterns[i]) < 0) {
+			upstream_pattern_list_clear(patterns, i);
+			die(_("'%s' is not a valid branch or pattern"), arg);
+		}
+	}
+	*patterns_out = patterns;
+	*nr_out = args->nr;
+}
+
+static int upstream_matches(const char *short_upstream,
+			    const struct upstream_pattern *patterns,
+			    size_t nr)
+{
+	size_t i;
+
+	for (i = 0; i < nr; i++) {
+		const struct upstream_pattern *p = &patterns[i];
+		if (p->is_wildcard) {
+			if (!wildmatch(p->name, short_upstream, WM_PATHNAME))
+				return 1;
+		} else if (!strcmp(p->name, short_upstream)) {
+			return 1;
+		}
+	}
+	return 0;
+}
+
+static int branch_upstream_matches(const char *short_branch_name,
+				   const struct upstream_pattern *patterns,
+				   size_t nr_patterns)
+{
+	struct branch *branch = branch_get(short_branch_name);
+	const char *upstream;
+
+	if (!branch)
+		return 0;
+	upstream = branch_get_upstream(branch, NULL);
+	if (!upstream)
+		return 0;
+	return upstream_matches(short_upstream_name(upstream),
+				patterns, nr_patterns);
+}
+
+static void filter_array_by_forked(struct ref_array *array,
+				   const struct string_list *upstreams)
+{
+	struct upstream_pattern *patterns = NULL;
+	size_t nr_patterns = 0;
+	int i, kept = 0;
+
+	parse_forked_args(upstreams, &patterns, &nr_patterns);
+
+	for (i = 0; i < array->nr; i++) {
+		struct ref_array_item *item = array->items[i];
+		const char *short_name;
+		if (skip_prefix(item->refname, "refs/heads/", &short_name) &&
+		    branch_upstream_matches(short_name, patterns, nr_patterns))
+			array->items[kept++] = item;
+		else
+			free_ref_array_item(item);
+	}
+	array->nr = kept;
+
+	upstream_pattern_list_clear(patterns, nr_patterns);
+}
+
+struct forked_cb {
+	const struct upstream_pattern *patterns;
+	size_t nr_patterns;
+	struct string_list *out;
+};
+
+static int collect_forked_branch(const struct reference *ref, void *cb_data)
+{
+	struct forked_cb *cb = cb_data;
+
+	if (ref->flags & REF_ISSYMREF)
+		return 0;
+	if (branch_upstream_matches(ref->name, cb->patterns, cb->nr_patterns))
+		string_list_append(cb->out, ref->name);
+	return 0;
+}
+
+static void collect_forked_set(const struct string_list *upstreams,
+			       struct string_list *out)
+{
+	struct upstream_pattern *patterns = NULL;
+	size_t nr_patterns = 0;
+	struct forked_cb cb;
+
+	parse_forked_args(upstreams, &patterns, &nr_patterns);
+	cb.patterns = patterns;
+	cb.nr_patterns = nr_patterns;
+	cb.out = out;
+
+	refs_for_each_branch_ref(get_main_ref_store(the_repository),
+				 collect_forked_branch, &cb);
+
+	string_list_sort(out);
+
+	upstream_pattern_list_clear(patterns, nr_patterns);
+}
+
+static int prune_merged_branches(const struct string_list *upstreams,
+				 int quiet, int dry_run)
+{
+	struct ref_store *refs = get_main_ref_store(the_repository);
+	struct string_list candidates = STRING_LIST_INIT_DUP;
+	struct strvec deletable = STRVEC_INIT;
+	struct string_list_item *item;
+	int ret = 0;
+
+	if (!upstreams->nr)
+		die(_("--prune-merged requires at least one <branch>"));
+
+	collect_forked_set(upstreams, &candidates);
+
+	for_each_string_list_item(item, &candidates) {
+		const char *short_name = item->string;
+		struct branch *branch = branch_get(short_name);
+		const char *upstream, *push;
+		struct strbuf full = STRBUF_INIT;
+		struct strbuf key = STRBUF_INIT;
+		int skip;
+		int opt_out;
+
+		strbuf_addf(&full, "refs/heads/%s", short_name);
+		skip = !!branch_checked_out(full.buf);
+		strbuf_release(&full);
+		if (skip)
+			continue;
+
+		upstream = branch ? branch_get_upstream(branch, NULL) : NULL;
+		if (!upstream || !refs_ref_exists(refs, upstream))
+			continue;
+		push = branch ? branch_get_push(branch, NULL) : NULL;
+		if (!push || !strcmp(push, upstream))
+			continue;
+
+		strbuf_addf(&key, "branch.%s.prunemerged", short_name);
+		if (!repo_config_get_bool(the_repository, key.buf, &opt_out) &&
+		    !opt_out) {
+			if (!quiet)
+				fprintf(stderr,
+					_("Skipping '%s' (branch.%s.pruneMerged is false)\n"),
+					short_name, short_name);
+			strbuf_release(&key);
+			continue;
+		}
+		strbuf_release(&key);
+
+		strvec_push(&deletable, short_name);
+	}
+
+	if (deletable.nr)
+		ret = delete_branches(deletable.nr, deletable.v,
+				      0, /* force */
+				      FILTER_REFS_BRANCHES,
+				      quiet,
+				      1, /* warn_only */
+				      1, /* no_head_fallback */
+				      dry_run);
+
+	strvec_clear(&deletable);
+	string_list_clear(&candidates, 0);
+	return ret;
+}
+
 static GIT_PATH_FUNC(edit_description, "EDIT_DESCRIPTION")
 
 static int edit_branch_description(const char *branch_name)
@@ -714,6 +965,9 @@ int cmd_branch(int argc,
 	/* possible actions */
 	int delete = 0, rename = 0, copy = 0, list = 0,
 	    unset_upstream = 0, show_current = 0, edit_description = 0;
+	struct string_list forked_upstreams = STRING_LIST_INIT_DUP;
+	struct string_list prune_merged_upstreams = STRING_LIST_INIT_DUP;
+	int dry_run = 0;
 	const char *new_upstream = NULL;
 	int noncreate_actions = 0;
 	/* possible options */
@@ -767,6 +1021,12 @@ int cmd_branch(int argc,
 		OPT_BOOL(0, "create-reflog", &reflog, N_("create the branch's reflog")),
 		OPT_BOOL(0, "edit-description", &edit_description,
 			 N_("edit the description for the branch")),
+		OPT_STRING_LIST(0, "forked", &forked_upstreams, N_("branch"),
+			N_("list local branches whose upstream matches <branch> (repeatable)")),
+		OPT_STRING_LIST(0, "prune-merged", &prune_merged_upstreams, N_("branch"),
+			N_("delete local branches whose upstream matches <branch> and is merged (repeatable)")),
+		OPT_BOOL(0, "dry-run", &dry_run,
+			N_("with --prune-merged, only print which branches would be deleted")),
 		OPT__FORCE(&force, N_("force creation, move/rename, deletion"), PARSE_OPT_NOCOMPLETE),
 		OPT_MERGED(&filter, N_("print only branches that are merged")),
 		OPT_NO_MERGED(&filter, N_("print only branches that are not merged")),
@@ -811,19 +1071,24 @@ int cmd_branch(int argc,
 			     0);
 
 	if (!delete && !rename && !copy && !edit_description && !new_upstream &&
-	    !show_current && !unset_upstream && argc == 0)
+	    !show_current && !unset_upstream && !prune_merged_upstreams.nr &&
+	    argc == 0)
 		list = 1;
 
 	if (filter.with_commit || filter.no_commit ||
-	    filter.reachable_from || filter.unreachable_from || filter.points_at.nr)
+	    filter.reachable_from || filter.unreachable_from ||
+	    filter.points_at.nr || forked_upstreams.nr)
 		list = 1;
 
 	noncreate_actions = !!delete + !!rename + !!copy + !!new_upstream +
 			    !!show_current + !!list + !!edit_description +
-			    !!unset_upstream;
+			    !!unset_upstream + !!prune_merged_upstreams.nr;
 	if (noncreate_actions > 1)
 		usage_with_options(builtin_branch_usage, options);
 
+	if (dry_run && !prune_merged_upstreams.nr)
+		die(_("--dry-run requires --prune-merged"));
+
 	if (recurse_submodules_explicit) {
 		if (!submodule_propagate_branches)
 			die(_("branch with --recurse-submodules can only be used if submodule.propagateBranches is enabled"));
@@ -858,7 +1123,14 @@ int cmd_branch(int argc,
 	if (delete) {
 		if (!argc)
 			die(_("branch name required"));
-		ret = delete_branches(argc, argv, delete > 1, filter.kind, quiet);
+		ret = delete_branches(argc, argv, delete > 1, filter.kind,
+				      quiet, 0, 0, 0);
+		goto out;
+	} else if (prune_merged_upstreams.nr) {
+		if (argc)
+			die(_("--prune-merged does not take positional arguments; "
+			      "repeat --prune-merged for each <branch>"));
+		ret = prune_merged_branches(&prune_merged_upstreams, quiet, dry_run);
 		goto out;
 	} else if (show_current) {
 		print_current_branch_name();
@@ -880,7 +1152,8 @@ int cmd_branch(int argc,
 		ref_sorting_set_sort_flags_all(sorting, REF_SORTING_ICASE, icase);
 		ref_sorting_set_sort_flags_all(
 			sorting, REF_SORTING_DETACHED_HEAD_FIRST, 1);
-		print_ref_list(&filter, sorting, &format, &output);
+		print_ref_list(&filter, sorting, &format, &output,
+			       &forked_upstreams);
 		print_columns(&output, colopts, NULL);
 		string_list_clear(&output, 0);
 		ref_sorting_release(sorting);
@@ -1020,5 +1293,7 @@ int cmd_branch(int argc,
 
 out:
 	string_list_clear(&sorting_options, 0);
+	string_list_clear(&forked_upstreams, 0);
+	string_list_clear(&prune_merged_upstreams, 0);
 	return ret;
 }
diff --git a/ref-filter.c b/ref-filter.c
index 1da4c0e60d..65e7bc6785 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -3035,7 +3035,7 @@ static int filter_one(const struct reference *ref, void *cb_data)
 }
 
 /*  Free memory allocated for a ref_array_item */
-static void free_array_item(struct ref_array_item *item)
+void free_ref_array_item(struct ref_array_item *item)
 {
 	free((char *)item->symref);
 	if (item->value) {
@@ -3078,7 +3078,7 @@ static int filter_and_format_one(const struct reference *ref, void *cb_data)
 
 	strbuf_release(&output);
 	strbuf_release(&err);
-	free_array_item(item);
+	free_ref_array_item(item);
 
 	/*
 	 * Increment the running count of refs that match the filter. If
@@ -3098,7 +3098,7 @@ void ref_array_clear(struct ref_array *array)
 	int i;
 
 	for (i = 0; i < array->nr; i++)
-		free_array_item(array->items[i]);
+		free_ref_array_item(array->items[i]);
 	FREE_AND_NULL(array->items);
 	array->nr = array->alloc = 0;
 
@@ -3171,7 +3171,7 @@ static void reach_filter(struct ref_array *array,
 		if (is_merged == include_reached)
 			array->items[array->nr++] = array->items[i];
 		else
-			free_array_item(item);
+			free_ref_array_item(item);
 	}
 
 	clear_commit_marks_many(old_nr, to_clear, ALL_REV_FLAGS);
@@ -3667,7 +3667,7 @@ void pretty_print_ref(const char *name, const struct object_id *oid,
 
 	strbuf_release(&err);
 	strbuf_release(&output);
-	free_array_item(ref_item);
+	free_ref_array_item(ref_item);
 }
 
 static int parse_sorting_atom(const char *atom)
diff --git a/ref-filter.h b/ref-filter.h
index 120221b47f..3883b9dc62 100644
--- a/ref-filter.h
+++ b/ref-filter.h
@@ -155,6 +155,8 @@ void filter_and_format_refs(struct ref_filter *filter, unsigned int type,
 			    struct ref_format *format);
 /*  Clear all memory allocated to ref_array */
 void ref_array_clear(struct ref_array *array);
+/*  Free a single item from a ref_array */
+void free_ref_array_item(struct ref_array_item *item);
 /*  Used to verify if the given format is correct and to parse out the used atoms */
 int verify_ref_format(struct ref_format *format);
 /*  Sort the given ref_array as per the ref_sorting provided */
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index 5f8a31c21d..84fefdb610 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -1719,4 +1719,358 @@ test_expect_success 'errors if given a bad branch name' '
 	test_cmp expect actual
 '
 
+test_expect_success '--forked: setup' '
+	test_create_repo forked-upstream &&
+	test_commit -C forked-upstream base &&
+	git -C forked-upstream branch one base &&
+	git -C forked-upstream branch two base &&
+
+	test_create_repo forked-other &&
+	test_commit -C forked-other other-base &&
+	git -C forked-other branch foreign other-base &&
+
+	git clone forked-upstream forked &&
+	git -C forked remote add other ../forked-other &&
+	git -C forked fetch other &&
+	git -C forked branch local-base &&
+	git -C forked branch --track local-one origin/one &&
+	git -C forked branch --track local-two origin/two &&
+	git -C forked branch --track local-foreign other/foreign &&
+	git -C forked branch detached &&
+	git -C forked branch --track local-trunk local-base
+'
+
+test_expect_success '--forked <upstream-tracking-branch> filters by upstream' '
+	git -C forked branch --forked origin/one --format="%(refname:short)" >actual &&
+	echo local-one >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '--forked <glob> filters by wildmatch' '
+	git -C forked branch --forked "origin/*" --format="%(refname:short)" >actual &&
+	cat >expect <<-\EOF &&
+	local-one
+	local-two
+	main
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success '--forked <local-branch> matches branches with local upstream' '
+	git -C forked branch --forked local-base --format="%(refname:short)" >actual &&
+	echo local-trunk >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '--forked can be repeated to widen the filter' '
+	git -C forked branch --forked origin/one --forked other/foreign --format="%(refname:short)" >actual &&
+	cat >expect <<-\EOF &&
+	local-foreign
+	local-one
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success '--forked combines literal and glob arguments' '
+	git -C forked branch --forked local-base --forked "other/*" --format="%(refname:short)" >actual &&
+	cat >expect <<-\EOF &&
+	local-foreign
+	local-trunk
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success '--forked "*/*" covers every remote-tracking upstream' '
+	git -C forked branch --forked "*/*" --format="%(refname:short)" >actual &&
+	cat >expect <<-\EOF &&
+	local-foreign
+	local-one
+	local-two
+	main
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success '--forked composes with --no-merged' '
+	test_when_finished "git -C forked checkout detached" &&
+	git -C forked checkout local-one &&
+	test_commit -C forked local-only &&
+	git -C forked branch --forked "origin/*" --no-merged origin/one \
+		--format="%(refname:short)" >actual &&
+	echo local-one >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '--forked rejects unknown branch/pattern' '
+	test_must_fail git -C forked branch --forked nope 2>err &&
+	test_grep "not a valid branch or pattern" err
+'
+
+test_expect_success '--forked requires a value' '
+	test_must_fail git -C forked branch --forked 2>err &&
+	test_grep "requires a value" err
+'
+
+test_expect_success '--prune-merged: setup' '
+	test_create_repo pm-upstream &&
+	test_commit -C pm-upstream base &&
+	git -C pm-upstream checkout -b next &&
+	test_commit -C pm-upstream one-commit &&
+	test_commit -C pm-upstream two-commit &&
+	git -C pm-upstream branch one HEAD~ &&
+	git -C pm-upstream branch two HEAD &&
+	git -C pm-upstream branch wip main &&
+	git -C pm-upstream checkout main &&
+	test_create_repo pm-fork
+'
+
+test_expect_success '--prune-merged deletes branches integrated into upstream' '
+	test_when_finished "rm -rf pm-merged" &&
+	git clone pm-upstream pm-merged &&
+	git -C pm-merged remote add fork ../pm-fork &&
+	test_config -C pm-merged remote.pushDefault fork &&
+	test_config -C pm-merged push.default current &&
+	git -C pm-merged branch one one-commit &&
+	git -C pm-merged branch --set-upstream-to=origin/next one &&
+	git -C pm-merged branch two two-commit &&
+	git -C pm-merged branch --set-upstream-to=origin/next two &&
+
+	git -C pm-merged branch --prune-merged "origin/*" &&
+
+	test_must_fail git -C pm-merged rev-parse --verify refs/heads/one &&
+	test_must_fail git -C pm-merged rev-parse --verify refs/heads/two
+'
+
+test_expect_success '--prune-merged accepts a literal upstream' '
+	test_when_finished "rm -rf pm-literal" &&
+	git clone pm-upstream pm-literal &&
+	git -C pm-literal remote add fork ../pm-fork &&
+	test_config -C pm-literal remote.pushDefault fork &&
+	test_config -C pm-literal push.default current &&
+	git -C pm-literal branch one one-commit &&
+	git -C pm-literal branch --set-upstream-to=origin/next one &&
+
+	git -C pm-literal branch --prune-merged origin/next &&
+
+	test_must_fail git -C pm-literal rev-parse --verify refs/heads/one
+'
+
+test_expect_success '--prune-merged unions multiple <branch> arguments' '
+	test_when_finished "rm -rf pm-union" &&
+	git clone pm-upstream pm-union &&
+	git -C pm-union remote add fork ../pm-fork &&
+	test_config -C pm-union remote.pushDefault fork &&
+	test_config -C pm-union push.default current &&
+	git -C pm-union branch one one-commit &&
+	git -C pm-union branch --set-upstream-to=origin/next one &&
+	git -C pm-union branch two base &&
+	git -C pm-union branch --set-upstream-to=origin/main two &&
+	git -C pm-union checkout --detach &&
+
+	git -C pm-union branch --prune-merged origin/next --prune-merged origin/main &&
+
+	test_must_fail git -C pm-union rev-parse --verify refs/heads/one &&
+	test_must_fail git -C pm-union rev-parse --verify refs/heads/two
+'
+
+test_expect_success '--prune-merged accepts a local upstream' '
+	test_when_finished "rm -rf pm-local" &&
+	git clone pm-upstream pm-local &&
+	git -C pm-local remote add fork ../pm-fork &&
+	test_config -C pm-local remote.pushDefault fork &&
+	test_config -C pm-local push.default current &&
+	git -C pm-local checkout -b trunk &&
+	git -C pm-local branch one one-commit &&
+	git -C pm-local branch --set-upstream-to=trunk one &&
+	git -C pm-local merge --ff-only one-commit &&
+
+	git -C pm-local branch --prune-merged trunk &&
+
+	test_must_fail git -C pm-local rev-parse --verify refs/heads/one
+'
+
+test_expect_success '--prune-merged warns instead of erroring on un-integrated commits' '
+	test_when_finished "rm -rf pm-unmerged" &&
+	git clone pm-upstream pm-unmerged &&
+	git -C pm-unmerged remote add fork ../pm-fork &&
+	test_config -C pm-unmerged remote.pushDefault fork &&
+	test_config -C pm-unmerged push.default current &&
+	git -C pm-unmerged checkout -b wip origin/wip &&
+	git -C pm-unmerged branch --set-upstream-to=origin/next wip &&
+	test_commit -C pm-unmerged local-only &&
+	git -C pm-unmerged checkout - &&
+
+	git -C pm-unmerged branch --prune-merged "origin/*" 2>err &&
+	test_grep "not fully merged" err &&
+	test_grep ! "If you are sure you want to delete it" err &&
+	git -C pm-unmerged rev-parse --verify refs/heads/wip
+'
+
+test_expect_success '--prune-merged is silent about not-merged-to-HEAD' '
+	test_when_finished "rm -rf pm-nohead" &&
+	git clone pm-upstream pm-nohead &&
+	git -C pm-nohead remote add fork ../pm-fork &&
+	test_config -C pm-nohead remote.pushDefault fork &&
+	test_config -C pm-nohead push.default current &&
+	git -C pm-nohead branch topic one-commit &&
+	git -C pm-nohead branch --set-upstream-to=origin/next topic &&
+
+	git -C pm-nohead branch --prune-merged "origin/*" 2>err &&
+
+	test_grep ! "not yet merged to HEAD" err &&
+	test_must_fail git -C pm-nohead rev-parse --verify refs/heads/topic
+'
+
+test_expect_success '--prune-merged skips branches whose upstream is gone' '
+	test_when_finished "rm -rf pm-upstream-gone" &&
+	git clone pm-upstream pm-upstream-gone &&
+	git -C pm-upstream-gone remote add fork ../pm-fork &&
+	test_config -C pm-upstream-gone remote.pushDefault fork &&
+	test_config -C pm-upstream-gone push.default current &&
+	git -C pm-upstream-gone branch one one-commit &&
+	git -C pm-upstream-gone branch --set-upstream-to=origin/next one &&
+
+	git -C pm-upstream-gone update-ref -d refs/remotes/origin/next &&
+	git -C pm-upstream-gone branch --prune-merged "origin/*" &&
+
+	git -C pm-upstream-gone rev-parse --verify refs/heads/one
+'
+
+test_expect_success '--prune-merged never deletes the checked-out branch' '
+	test_when_finished "rm -rf pm-head" &&
+	git clone pm-upstream pm-head &&
+	git -C pm-head remote add fork ../pm-fork &&
+	test_config -C pm-head remote.pushDefault fork &&
+	test_config -C pm-head push.default current &&
+	git -C pm-head checkout -b one one-commit &&
+	git -C pm-head branch --set-upstream-to=origin/next one &&
+
+	git -C pm-head branch --prune-merged "origin/*" &&
+
+	git -C pm-head rev-parse --verify refs/heads/one
+'
+
+test_expect_success '--prune-merged spares branches that push back to their upstream' '
+	test_when_finished "rm -rf pm-push-eq" &&
+	git clone pm-upstream pm-push-eq &&
+	git -C pm-push-eq checkout --detach &&
+
+	git -C pm-push-eq branch --prune-merged "origin/*" &&
+
+	git -C pm-push-eq rev-parse --verify refs/heads/main
+'
+
+test_expect_success '--prune-merged spares a per-branch pushRemote==upstream remote' '
+	test_when_finished "rm -rf pm-push-branch" &&
+	git clone pm-upstream pm-push-branch &&
+	git -C pm-push-branch remote add fork ../pm-fork &&
+	test_config -C pm-push-branch remote.pushDefault fork &&
+	test_config -C pm-push-branch push.default current &&
+	test_config -C pm-push-branch branch.main.pushRemote origin &&
+	git -C pm-push-branch checkout --detach &&
+
+	git -C pm-push-branch branch --prune-merged "origin/*" &&
+
+	git -C pm-push-branch rev-parse --verify refs/heads/main
+'
+
+test_expect_success '--prune-merged prunes when @{push} differs from @{upstream}' '
+	test_when_finished "rm -rf pm-push-diff" &&
+	git clone pm-upstream pm-push-diff &&
+	git -C pm-push-diff remote add fork ../pm-fork &&
+	test_config -C pm-push-diff remote.pushDefault fork &&
+	test_config -C pm-push-diff push.default current &&
+	git -C pm-push-diff branch topic one-commit &&
+	git -C pm-push-diff branch --set-upstream-to=origin/next topic &&
+	git -C pm-push-diff checkout --detach &&
+
+	git -C pm-push-diff branch --prune-merged "origin/*" &&
+
+	test_must_fail git -C pm-push-diff rev-parse --verify refs/heads/topic
+'
+
+test_expect_success '--prune-merged requires a value' '
+	test_must_fail git -C forked branch --prune-merged 2>err &&
+	test_grep "requires a value" err
+'
+
+test_expect_success '--prune-merged rejects positional arguments' '
+	test_must_fail git -C forked branch --prune-merged origin/one other/foreign 2>err &&
+	test_grep "does not take positional arguments" err
+'
+
+test_expect_success '--prune-merged honours branch.<name>.pruneMerged=false' '
+	test_when_finished "rm -rf pm-optout" &&
+	git clone pm-upstream pm-optout &&
+	git -C pm-optout remote add fork ../pm-fork &&
+	test_config -C pm-optout remote.pushDefault fork &&
+	test_config -C pm-optout push.default current &&
+	git -C pm-optout branch one one-commit &&
+	git -C pm-optout branch --set-upstream-to=origin/next one &&
+	git -C pm-optout branch two two-commit &&
+	git -C pm-optout branch --set-upstream-to=origin/next two &&
+	test_config -C pm-optout branch.one.pruneMerged false &&
+
+	git -C pm-optout branch --prune-merged "origin/*" 2>err &&
+
+	git -C pm-optout rev-parse --verify refs/heads/one &&
+	test_must_fail git -C pm-optout rev-parse --verify refs/heads/two &&
+	test_grep "Skipping .one." err
+'
+
+test_expect_success 'branch -d still deletes a pruneMerged=false branch' '
+	test_when_finished "rm -rf pm-optout-d" &&
+	git clone pm-upstream pm-optout-d &&
+	git -C pm-optout-d branch one one-commit &&
+	git -C pm-optout-d branch --set-upstream-to=origin/next one &&
+	test_config -C pm-optout-d branch.one.pruneMerged false &&
+
+	git -C pm-optout-d branch -d one &&
+	test_must_fail git -C pm-optout-d rev-parse --verify refs/heads/one
+'
+
+test_expect_success '--prune-merged --dry-run lists but does not delete' '
+	test_when_finished "rm -rf pm-dry" &&
+	git clone pm-upstream pm-dry &&
+	git -C pm-dry remote add fork ../pm-fork &&
+	test_config -C pm-dry remote.pushDefault fork &&
+	test_config -C pm-dry push.default current &&
+	git -C pm-dry branch one one-commit &&
+	git -C pm-dry branch --set-upstream-to=origin/next one &&
+	git -C pm-dry branch two two-commit &&
+	git -C pm-dry branch --set-upstream-to=origin/next two &&
+
+	git -C pm-dry branch --dry-run --prune-merged "origin/*" >actual &&
+	test_grep "Would delete branch one " actual &&
+	test_grep "Would delete branch two " actual &&
+
+	git -C pm-dry rev-parse --verify refs/heads/one &&
+	git -C pm-dry rev-parse --verify refs/heads/two
+'
+
+test_expect_success '--prune-merged --dry-run only lists branches the live run would delete' '
+	test_when_finished "rm -rf pm-dry-mixed" &&
+	git clone pm-upstream pm-dry-mixed &&
+	git -C pm-dry-mixed remote add fork ../pm-fork &&
+	test_config -C pm-dry-mixed remote.pushDefault fork &&
+	test_config -C pm-dry-mixed push.default current &&
+	git -C pm-dry-mixed checkout -b wip origin/next &&
+	git -C pm-dry-mixed branch --set-upstream-to=origin/next wip &&
+	test_commit -C pm-dry-mixed local-only &&
+	git -C pm-dry-mixed checkout - &&
+	git -C pm-dry-mixed branch merged one-commit &&
+	git -C pm-dry-mixed branch --set-upstream-to=origin/next merged &&
+
+	git -C pm-dry-mixed branch --dry-run --prune-merged "origin/*" >out &&
+	test_grep "Would delete branch merged" out &&
+	test_grep ! "Would delete branch wip" out &&
+	git -C pm-dry-mixed rev-parse --verify refs/heads/wip &&
+	git -C pm-dry-mixed rev-parse --verify refs/heads/merged
+'
+
+test_expect_success '--dry-run without --prune-merged is rejected' '
+	test_must_fail git -C forked branch --dry-run 2>err &&
+	test_grep "requires --prune-merged" err
+'
+
 test_done