Export of internal Abseil changes

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bcd349230e418f5e29d5fced1b942828fa5cb2ad by Abseil Team <absl-team@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 436317331
Change-Id: I0f8a0c4cd0d5f348a33e486c85c863072c30742a
GitOrigin-RevId: bcd349230e418f5e29d5fced1b942828fa5cb2ad

absl/time/internal/cctz/src/time_zone_lookup_test.cc

diff --git a/absl/time/internal/cctz/src/time_zone_lookup_test.cc b/absl/time/internal/cctz/src/time_zone_lookup_test.cc
index 0226ab7..134d143 100644
--- a/absl/time/internal/cctz/src/time_zone_lookup_test.cc
+++ b/absl/time/internal/cctz/src/time_zone_lookup_test.cc
@@ -1182,6 +1182,44 @@
   // We have a transition but we don't know which one.
 }
 
+TEST(NextTransition, Scan) {
+  for (const char* const* np = kTimeZoneNames; *np != nullptr; ++np) {
+    time_zone tz;
+    if (!load_time_zone(*np, &tz)) {
+      continue;  // tolerate kTimeZoneNames/zoneinfo skew
+    }
+    SCOPED_TRACE(testing::Message() << "In " << *np);
+
+    auto tp = time_point<absl::time_internal::cctz::seconds>::min();
+    time_zone::civil_transition trans;
+    while (tz.next_transition(tp, &trans)) {
+      time_zone::civil_lookup from_cl = tz.lookup(trans.from);
+      EXPECT_NE(from_cl.kind, time_zone::civil_lookup::REPEATED);
+      time_zone::civil_lookup to_cl = tz.lookup(trans.to);
+      EXPECT_NE(to_cl.kind, time_zone::civil_lookup::SKIPPED);
+
+      auto trans_tp = to_cl.trans;
+      time_zone::absolute_lookup trans_al = tz.lookup(trans_tp);
+      EXPECT_EQ(trans_al.cs, trans.to);
+      auto pre_trans_tp = trans_tp - absl::time_internal::cctz::seconds(1);
+      time_zone::absolute_lookup pre_trans_al = tz.lookup(pre_trans_tp);
+      EXPECT_EQ(pre_trans_al.cs + 1, trans.from);
+
+      auto offset_delta = trans_al.offset - pre_trans_al.offset;
+      EXPECT_EQ(offset_delta, trans.to - trans.from);
+      if (offset_delta == 0) {
+        // This "transition" is only an is_dst or abbr change.
+        EXPECT_EQ(to_cl.kind, time_zone::civil_lookup::UNIQUE);
+        if (trans_al.is_dst == pre_trans_al.is_dst) {
+          EXPECT_STRNE(trans_al.abbr, pre_trans_al.abbr);
+        }
+      }
+
+      tp = trans_tp;  // continue scan from transition
+    }
+  }
+}
+
 TEST(TimeZoneEdgeCase, AmericaNewYork) {
   const time_zone tz = LoadZone("America/New_York");
 

absl/time/internal/cctz/testdata/README.zoneinfo

diff --git a/absl/time/internal/cctz/testdata/README.zoneinfo b/absl/time/internal/cctz/testdata/README.zoneinfo
index 95fb4a9..a41c7b8 100644
--- a/absl/time/internal/cctz/testdata/README.zoneinfo
+++ b/absl/time/internal/cctz/testdata/README.zoneinfo
@@ -13,7 +13,12 @@
   trap "rm -fr ${DESTDIR}" 0 2 15
   (
     cd ${DESTDIR}
-    git clone https://github.com/eggert/tz.git
+    if [ -n "${USE_GLOBAL_TZ}" ]
+    then
+      git clone -b global-tz https://github.com/JodaOrg/global-tz.git tz
+    else
+      git clone https://github.com/eggert/tz.git
+    fi
     make --directory=tz \
         install DESTDIR=${DESTDIR} \
                 DATAFORM=vanguard \