From 377444b440eab3b6ef636df092f7f8299acf75bb Mon Sep 17 00:00:00 2001
From: Derrick Stolee <dstolee@microsoft.com>
Date: Tue, 18 Jun 2019 13:25:27 -0700
Subject: fetch: warn about forced updates in branch listing

The --[no-]show-forced-updates option in 'git fetch' can be confusing
for some users, especially if it is enabled via config setting and not
by argument. Add advice to warn the user that the (forced update)
messages were not listed.

Additionally, warn users when the forced update check takes longer
than ten seconds, and recommend that they disable the check. These
messages can be disabled by the advice.fetchShowForcedUpdates config
setting.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/config/advice.txt b/Documentation/config/advice.txt
index ec4f6ae..1f1e847 100644
--- a/Documentation/config/advice.txt
+++ b/Documentation/config/advice.txt
@@ -4,6 +4,10 @@ advice.*::
 	can tell Git that you do not need help by setting these to 'false':
 +
 --
+	fetchShowForcedUpdates::
+		Advice shown when linkgit:git-fetch[1] takes a long time
+		to calculate forced updates after ref updates, or to warn
+		that the check is disabled.
 	pushUpdateRejected::
 		Set this variable to 'false' if you want to disable
 		'pushNonFFCurrent',
diff --git a/advice.c b/advice.c
index ce5f374..4b283be 100644
--- a/advice.c
+++ b/advice.c
@@ -3,6 +3,7 @@
 #include "color.h"
 #include "help.h"
 
+int advice_fetch_show_forced_updates = 1;
 int advice_push_update_rejected = 1;
 int advice_push_non_ff_current = 1;
 int advice_push_non_ff_matching = 1;
@@ -59,6 +60,7 @@ static struct {
 	const char *name;
 	int *preference;
 } advice_config[] = {
+	{ "fetchShowForcedUpdates", &advice_fetch_show_forced_updates },
 	{ "pushUpdateRejected", &advice_push_update_rejected },
 	{ "pushNonFFCurrent", &advice_push_non_ff_current },
 	{ "pushNonFFMatching", &advice_push_non_ff_matching },
diff --git a/advice.h b/advice.h
index e50f02c..495e532 100644
--- a/advice.h
+++ b/advice.h
@@ -3,6 +3,7 @@
 
 #include "git-compat-util.h"
 
+extern int advice_fetch_show_forced_updates;
 extern int advice_push_update_rejected;
 extern int advice_push_non_ff_current;
 extern int advice_push_non_ff_matching;
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 571c255..cf7eb0d 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -24,6 +24,8 @@
 #include "list-objects-filter-options.h"
 #include "commit-reach.h"
 
+#define FORCED_UPDATES_DELAY_WARNING_IN_MS (10 * 1000)
+
 static const char * const builtin_fetch_usage[] = {
 	N_("git fetch [<options>] [<repository> [<refspec>...]]"),
 	N_("git fetch [<options>] <group>"),
@@ -40,6 +42,7 @@ enum {
 
 static int fetch_prune_config = -1; /* unspecified */
 static int fetch_show_forced_updates = 1;
+static uint64_t forced_updates_ms = 0;
 static int prune = -1; /* unspecified */
 #define PRUNE_BY_DEFAULT 0 /* do we prune by default? */
 
@@ -707,6 +710,7 @@ static int update_local_ref(struct ref *ref,
 	enum object_type type;
 	struct branch *current_branch = branch_get(NULL);
 	const char *pretty_ref = prettify_refname(ref->name);
+	int fast_forward = 0;
 
 	type = oid_object_info(the_repository, &ref->new_oid, NULL);
 	if (type < 0)
@@ -781,7 +785,15 @@ static int update_local_ref(struct ref *ref,
 		return r;
 	}
 
-	if (!fetch_show_forced_updates || in_merge_bases(current, updated)) {
+	if (fetch_show_forced_updates) {
+		uint64_t t_before = getnanotime();
+		fast_forward = in_merge_bases(current, updated);
+		forced_updates_ms += (getnanotime() - t_before) / 1000000;
+	} else {
+		fast_forward = 1;
+	}
+
+	if (fast_forward) {
 		struct strbuf quickref = STRBUF_INIT;
 		int r;
 
@@ -980,6 +992,17 @@ static int store_updated_refs(const char *raw_url, const char *remote_name,
 		      " 'git remote prune %s' to remove any old, conflicting "
 		      "branches"), remote_name);
 
+	if (advice_fetch_show_forced_updates) {
+		if (!fetch_show_forced_updates) {
+			warning(_("Fetch normally indicates which branches had a forced update, but that check has been disabled."));
+			warning(_("To re-enable, use '--show-forced-updates' flag or run 'git config fetch.showForcedUpdates true'."));
+		} else if (forced_updates_ms > FORCED_UPDATES_DELAY_WARNING_IN_MS) {
+			warning(_("It took %.2f seconds to check forced updates. You can use '--no-show-forced-updates'\n"),
+				forced_updates_ms / 1000.0);
+			warning(_("or run 'git config fetch.showForcedUpdates false' to avoid this check.\n"));
+		}
+	}
+
  abort:
 	strbuf_release(&note);
 	free(url);
-- 
cgit v0.10.2-6-g49f6