[PATCH v14 4/6] branch: add --prune-merged <branch>

["Harald Nordgren via GitGitGadget" <gitgitgadget@gmail.com>]

From: Harald Nordgren <haraldnordgren@gmail.com>

	git branch --prune-merged <branch>...

deletes the local branches that "--forked <branch>" would list,
keeping only those whose tip is reachable from their configured
upstream: the work has already landed on the upstream they track,
so the local copy is no longer needed.

Reachability is read from local refs; nothing is fetched. Run
"git fetch" first if you want fresh upstream refs.

Three kinds of branches are spared:

  * any branch checked out in any worktree;
  * any branch whose upstream no longer resolves locally, since a
    missing upstream is not by itself a sign of integration;
  * any branch whose push destination equals its upstream
    (<branch>@{push} is the same as <branch>@{upstream}), such as
    a local "main" that tracks and pushes to "origin/main". Right
    after a pull it just looks "fully merged", so it is left
    alone. Only branches that push somewhere other than their
    upstream, typically topics in a fork workflow, are candidates.

Branches that are not yet merged into their upstream are reported
as a short warning and skipped, so one unmerged topic does not
abort the whole sweep.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
---
 Documentation/git-branch.adoc |  24 ++++
 builtin/branch.c              |  67 +++++++++++-
 t/t3200-branch.sh             | 201 ++++++++++++++++++++++++++++++++++
 3 files changed, 290 insertions(+), 2 deletions(-)

diff --git a/Documentation/git-branch.adoc b/Documentation/git-branch.adoc
index 62ebab6051..fdaccc9662 100644
--- a/Documentation/git-branch.adoc
+++ b/Documentation/git-branch.adoc
@@ -25,6 +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 --prune-merged <branch>...
 
 DESCRIPTION
 -----------
@@ -201,6 +202,29 @@ This option is only applicable in non-verbose mode.
 	Print the name of the current branch. In detached `HEAD` state,
 	nothing is printed.
 
+`--prune-merged <branch>...`::
+	Delete the local branches that `--forked` would list for the
+	given _<branch>_ arguments, 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. Several
+	_<branch>_ patterns may be given, e.g. `git branch
+	--prune-merged origin/main 'feature*'`.
++
+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; or 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".
++
+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.
+
 `-v`::
 `-vv`::
 `--verbose`::
diff --git a/builtin/branch.c b/builtin/branch.c
index 2cc5a8cde0..af37a0ceb7 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -38,6 +38,7 @@ 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
 };
 
@@ -715,6 +716,61 @@ static int parse_opt_forked(const struct option *opt, const char *arg, int unset
 	return 0;
 }
 
+static int prune_merged_branches(int argc, const char **argv,
+				 int quiet)
+{
+	struct ref_store *refs = get_main_ref_store(the_repository);
+	struct ref_filter filter = REF_FILTER_INIT;
+	struct ref_array candidates;
+	struct strvec deletable = STRVEC_INIT;
+	int i, ret = 0;
+
+	if (!argc)
+		die(_("--prune-merged requires at least one <branch>"));
+
+	for (i = 0; i < argc; i++)
+		if (ref_filter_forked_add(&filter, argv[i]) < 0)
+			die(_("'%s' is not a valid branch or pattern"), argv[i]);
+
+	filter.kind = FILTER_REFS_BRANCHES;
+	memset(&candidates, 0, sizeof(candidates));
+	filter_refs(&candidates, &filter, filter.kind);
+
+	for (i = 0; i < candidates.nr; i++) {
+		const char *full_name = candidates.items[i]->refname;
+		const char *short_name;
+		struct branch *branch;
+		const char *upstream, *push;
+
+		if (!skip_prefix(full_name, "refs/heads/", &short_name))
+			continue;
+		if (branch_checked_out(full_name))
+			continue;
+
+		branch = branch_get(short_name);
+		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;
+
+		strvec_push(&deletable, short_name);
+	}
+
+	if (deletable.nr)
+		ret = delete_branches(deletable.nr, deletable.v,
+				      FILTER_REFS_BRANCHES,
+				      DELETE_BRANCH_WARN_ONLY |
+				      DELETE_BRANCH_NO_HEAD_FALLBACK |
+				      (quiet ? DELETE_BRANCH_QUIET : 0));
+
+	strvec_clear(&deletable);
+	ref_array_clear(&candidates);
+	ref_filter_clear(&filter);
+	return ret;
+}
+
 static GIT_PATH_FUNC(edit_description, "EDIT_DESCRIPTION")
 
 static int edit_branch_description(const char *branch_name)
@@ -756,6 +812,7 @@ 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;
+	int prune_merged = 0;
 	const char *new_upstream = NULL;
 	int noncreate_actions = 0;
 	/* possible options */
@@ -809,6 +866,8 @@ 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_BOOL(0, "prune-merged", &prune_merged,
+			N_("delete local branches whose upstream matches <branch> and is merged")),
 		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")),
@@ -856,7 +915,8 @@ 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 &&
+	    argc == 0)
 		list = 1;
 
 	if (filter.with_commit || filter.no_commit ||
@@ -866,7 +926,7 @@ int cmd_branch(int argc,
 
 	noncreate_actions = !!delete + !!rename + !!copy + !!new_upstream +
 			    !!show_current + !!list + !!edit_description +
-			    !!unset_upstream;
+			    !!unset_upstream + !!prune_merged;
 	if (noncreate_actions > 1)
 		usage_with_options(builtin_branch_usage, options);
 
@@ -908,6 +968,9 @@ int cmd_branch(int argc,
 				      (delete > 1 ? DELETE_BRANCH_FORCE : 0) |
 				      (quiet ? DELETE_BRANCH_QUIET : 0));
 		goto out;
+	} else if (prune_merged) {
+		ret = prune_merged_branches(argc, argv, quiet);
+		goto out;
 	} else if (show_current) {
 		print_current_branch_name();
 		ret = 0;
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index 4e7deddc04..27ea1319bb 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -1809,4 +1809,205 @@ test_expect_success '--forked requires a value' '
 	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 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 at least one <branch>' '
+	test_must_fail git -C forked branch --prune-merged 2>err &&
+	test_grep "requires at least one <branch>" err
+'
+
+test_expect_success '--prune-merged takes positional <branch> arguments' '
+	test_when_finished "rm -rf pm-positional" &&
+	git clone pm-upstream pm-positional &&
+	git -C pm-positional remote add fork ../pm-fork &&
+	test_config -C pm-positional remote.pushDefault fork &&
+	test_config -C pm-positional push.default current &&
+	git -C pm-positional branch one one-commit &&
+	git -C pm-positional branch --set-upstream-to=origin/next one &&
+	git -C pm-positional branch two base &&
+	git -C pm-positional branch --set-upstream-to=origin/main two &&
+	git -C pm-positional checkout --detach &&
+
+	git -C pm-positional branch --prune-merged origin/next origin/main &&
+
+	test_must_fail git -C pm-positional rev-parse --verify refs/heads/one &&
+	test_must_fail git -C pm-positional rev-parse --verify refs/heads/two
+'
+
 test_done
-- 
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