[PATCH v2 4/6] fetch: add --prune-merged

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

From: Harald Nordgren <haraldnordgren@gmail.com>

After a successful fetch from a configured remote, run
'git branch --prune-merged <remote>' to delete local branches
whose push destination ref has just been pruned.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
---
 Documentation/fetch-options.adoc |  8 ++++++++
 builtin/fetch.c                  | 20 ++++++++++++++++++++
 t/t5510-fetch.sh                 | 31 +++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+)

diff --git a/Documentation/fetch-options.adoc b/Documentation/fetch-options.adoc
index 81a9d7f9bb..d863a9184e 100644
--- a/Documentation/fetch-options.adoc
+++ b/Documentation/fetch-options.adoc
@@ -185,6 +185,14 @@ See the PRUNING section below for more details.
 +
 See the PRUNING section below for more details.
 
+`--prune-merged`::
+	After a successful fetch, run `git branch --prune-merged
+	<remote>` for the fetched remote, deleting local branches
+	that fork from this remote and whose tip is reachable from
+	their upstream remote-tracking ref. See linkgit:git-branch[1]
+	for the exact selection rules. The currently checked-out
+	branch is always preserved.
+
 endif::git-pull[]
 
 ifndef::git-pull[]
diff --git a/builtin/fetch.c b/builtin/fetch.c
index a22c319467..5451bf3b5b 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -82,6 +82,8 @@ static int prune = -1; /* unspecified */
 static int prune_tags = -1; /* unspecified */
 #define PRUNE_TAGS_BY_DEFAULT 0 /* do we prune tags by default? */
 
+static int prune_merged;
+
 static int append, dry_run, force, keep, update_head_ok;
 static int write_fetch_head = 1;
 static int verbosity, deepen_relative, set_upstream, refetch;
@@ -2189,6 +2191,8 @@ static void add_options_to_argv(struct strvec *argv,
 		strvec_push(argv, prune ? "--prune" : "--no-prune");
 	if (prune_tags != -1)
 		strvec_push(argv, prune_tags ? "--prune-tags" : "--no-prune-tags");
+	if (prune_merged)
+		strvec_push(argv, "--prune-merged");
 	if (update_head_ok)
 		strvec_push(argv, "--update-head-ok");
 	if (force)
@@ -2382,6 +2386,15 @@ static inline void fetch_one_setup_partial(struct remote *remote,
 	return;
 }
 
+static int prune_merged_for_remote(const struct remote *remote)
+{
+	struct child_process cmd = CHILD_PROCESS_INIT;
+
+	cmd.git_cmd = 1;
+	strvec_pushl(&cmd.args, "branch", "--prune-merged", remote->name, NULL);
+	return run_command(&cmd);
+}
+
 static int fetch_one(struct remote *remote, int argc, const char **argv,
 		     int prune_tags_ok, int use_stdin_refspecs,
 		     const struct fetch_config *config,
@@ -2457,6 +2470,11 @@ static int fetch_one(struct remote *remote, int argc, const char **argv,
 	refspec_clear(&rs);
 	transport_disconnect(gtransport);
 	gtransport = NULL;
+
+	if (!exit_code && prune_merged && remote_via_config &&
+	    prune_merged_for_remote(remote))
+		exit_code = 1;
+
 	return exit_code;
 }
 
@@ -2520,6 +2538,8 @@ int cmd_fetch(int argc,
 			 N_("prune remote-tracking branches no longer on remote")),
 		OPT_BOOL('P', "prune-tags", &prune_tags,
 			 N_("prune local tags no longer on remote and clobber changed tags")),
+		OPT_BOOL(0, "prune-merged", &prune_merged,
+			 N_("after pruning, also delete local branches forked from this remote whose tips are reachable from their upstream")),
 		OPT_CALLBACK_F(0, "recurse-submodules", &recurse_submodules_cli, N_("on-demand"),
 			    N_("control recursive fetching of submodules"),
 			    PARSE_OPT_OPTARG, option_fetch_parse_recurse_submodules),
diff --git a/t/t5510-fetch.sh b/t/t5510-fetch.sh
index 6fe21e2b3a..b94fd2bda0 100755
--- a/t/t5510-fetch.sh
+++ b/t/t5510-fetch.sh
@@ -386,6 +386,37 @@ test_expect_success REFFILES 'fetch --prune fails to delete branches' '
 	)
 '
 
+test_expect_success 'fetch --prune-merged: setup' '
+	git init -b main fetch-pm-parent &&
+	test_commit -C fetch-pm-parent base
+'
+
+test_expect_success 'fetch --prune-merged deletes merged local branches' '
+	test_when_finished "rm -rf fetch-pm-clone" &&
+	git -C fetch-pm-parent branch one base &&
+	git clone fetch-pm-parent fetch-pm-clone &&
+	git -C fetch-pm-clone branch one --track origin/one &&
+	git -C fetch-pm-parent branch -D one &&
+
+	git -C fetch-pm-clone fetch --prune --prune-merged origin &&
+
+	test_must_fail git -C fetch-pm-clone rev-parse --verify refs/heads/one
+'
+
+test_expect_success 'fetch --prune-merged skips unmerged local branches' '
+	test_when_finished "rm -rf fetch-pm-unmerged" &&
+	git -C fetch-pm-parent branch two base &&
+	git clone fetch-pm-parent fetch-pm-unmerged &&
+	git -C fetch-pm-unmerged checkout -b two --track origin/two &&
+	test_commit -C fetch-pm-unmerged unpushed &&
+	git -C fetch-pm-unmerged checkout - &&
+	git -C fetch-pm-parent branch -D two &&
+
+	git -C fetch-pm-unmerged fetch --prune --prune-merged origin 2>err &&
+	test_grep "not fully merged" err &&
+	git -C fetch-pm-unmerged rev-parse --verify refs/heads/two
+'
+
 test_expect_success 'fetch --atomic works with a single branch' '
 	test_when_finished "rm -rf atomic" &&
 
-- 
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